So you remember how you played Mass Effect 2 on Normal difficulty and you didn't care about any armor and weapon upgrades or you didn't have any motivation to mine the planets for minerals? Turns out that's just an odd balance choice from Bioware for this standard difficulty, where all the focus is on the story and not the combat.  
 
When you play the same game on the hardest Insanity difficulty you will face a completely different balance and it will feel like you are playing a completely different game. Essentially there are two games in one in Mass Effect 2. 
 
If you come to Insanity from Normal it will be quite brutal at first (at least for my 30-level soldier class it was), but that's when you are forced to learn the mechanics of the combat for the first time. And that's when you start to care about the upgrades of the armor and the weapons that the game has to offer (to get all of them you will want to mine as many planets as will be required). You also start to care about the team stats, I actually retrained my Shepard I think around 5 times until I found the combination that worked the best for my style of play.  
  
The main focus of this other game that comes inside the same ME2 package is on combat and RPG elements, the combat is so challenging and satisfying that I can't stop playing the game although that's my second playthrough and I know the story and usually I would be doing this only to get the final achievements, but not this time. I have finished hiring everyone except Legion for my team now and I can't wait until this workday will be over and I will continue playing. 
 
I haven't really had this kind of experience with any other game before.  
 
Great job Bioware (and Christina Norman)! 

So you remember how you played Mass Effect 2 on Normal difficulty and you didn't care about any armor and weapon upgrades or you didn't have any motivation to mine the planets for minerals? Turns out that's just an odd balance choice from Bioware for this standard difficulty, where all the focus is on the story and not the combat.  
 
When you play the same game on the hardest Insanity difficulty you will face a completely different balance and it will feel like you are playing a completely different game. Essentially there are two games in one in Mass Effect 2. 
 
If you come to Insanity from Normal it will be quite brutal at first (at least for my 30-level soldier class it was), but that's when you are forced to learn the mechanics of the combat for the first time. And that's when you start to care about the upgrades of the armor and the weapons that the game has to offer (to get all of them you will want to mine as many planets as will be required). You also start to care about the team stats, I actually retrained my Shepard I think around 5 times until I found the combination that worked the best for my style of play.  
  
The main focus of this other game that comes inside the same ME2 package is on combat and RPG elements, the combat is so challenging and satisfying that I can't stop playing the game although that's my second playthrough and I know the story and usually I would be doing this only to get the final achievements, but not this time. I have finished hiring everyone except Legion for my team now and I can't wait until this workday will be over and I will continue playing. 
 
I haven't really had this kind of experience with any other game before.  
 
Great job Bioware (and Christina Norman)! 

Yeah, i also noticed a huge difference in the game itself, when i switched from Normal to Insanity. But i honestly didn't think that it was bad, it wasn't horribly difficult, except for at couple of spots (the first pretorian encounter was insane indeed). But yeah, it's very cool that the experience can differ that much when you are only changing the difficulty.

Definitely not playing this on insanity, even if there is 10 new games in there.

It felt that Bioware balanced this game with Insanity in mind.  I remember playing on Veteran the first time and thinking, "why the hell do they give you so many med-kits and ammo throughout the missions?"  Apparently, they were for people playing on Insanity.
 
A lot of the RPG elements in the combat don't even come into play until you bump the difficulty up to Insanity.  For example, choosing which weapon to use is actually important.  Fighting people with barriers and shields - the SMG whittles that down the fastest.  Have to deal with enemy armor - sniper rifle and shotgun are the way to go.  These tactics are especially important since ME2 now has limited ammo.  There is no need to waste precious sniper rifle bullets when half a SMG clip will deplete an enemy's entire barrier.  You also have to make sure that someone in your squad has warp, reave, incinerate, or incendiary ammo to deal with enemy regeneration.  These are just the few things that you need to consider when playing on the higher difficulty.
 
That being said, I don't think Insanity was that hard (at least for Infiltrator - I heard playing Adept can be a bitch sometimes).  Other third person cover-based shooters like Gears of War 2 and Uncharted 2 on their highest difficulties were much harder than ME2 on Insanity.  Playing on Insanity is a lot more fun and rewarding though, as all the features that the combat has to offer are put to good use.

I played it on Veteran all the way through the first time. I then played a second time to get the
nobody dies on suicide mission achievement. For that, I just chose Normal & then put it on
Casual at the end (you just mow right through it).
 
I read a lot of frustration on different forums about Insanity, so I watched a few youtube guides on
what to do (eg, Adept on Insanity), so I won't get annoyed with the game.  I was thinking of
running a new guy/gal through ME1 & then through ME2 on Insanity. However, at this point,
I might just run my current evil guy through ME2 on insanity & finish ME1 up later on instead. 
Plus, if any new adventures come out for ME2, I can roll with my next group of ME1 vets. I kind
of hope ME2 comes out with an expansion pack like DA:O is doing.

I dont wanna sound like a douche, but insanity isnt very insane. Completed it with pretty much every class except for Sentinel with fresh characters (IE no level 30 chars). The flaw is that the AI doesnt become smarter. Its all about increased incoming damage. Dont ask me why I completed it so many times. Just kinda happend as I wanted to see alternative ways to go through the game and find small pieces of content that I missed (theres alot of small details that you miss easily).

If you are really worried about getting frustrated go as a sentinel, infiltrator or soldier.  Yea, I didnt complete it with the sentinel as it felt too easy and the class is boring.
Engineer is an alright class. No layers of protection to worry about.
Adepts requires you to utilize your squad abilities when shielded enemies appear (and to decrease the feeling of hitting Warp all the time).
Vanguards requires you to fully utilize your squad as they are weak against protective layers. Make sure you pick the right bonus-power aswell (reave is really nice). Avoid the temptation of hitting the cool, but suicidal biotic charge button.
 
Since you get a bonus power you should consider: reave and dominate depending on class.

mass effect 2 insanity is not really insane. as a matter of fact, it is all about barrier, armor, boosting shield when you face with enemies which have little more aggressive. that's all. tactic? I never feel I have to do. I beat this game over 31 times (15 times for insanity, for 16 times, vateran, hardcore level).  when it comes to insanity level, AI seems to improve dramatically. plus, I don't worry about upgrade because I am perfectionist who complete everything no matter what kind of level. so I get used to it. if you really want to experience what gaming level goes insane. then try Dead space hard level. you will know what I mean. you will throw out keyboard or gamepad whatever. 
 
I really want Bioware to make real insanity level for ME 3. come on, I don't think that multi layer of shield, barrier of enemies don't make this game any insane on that level. it's all about AI improvement. more aggressive, very tactical like Shepard, and squad members do.   

I played it on the difficulty right below Insanity and had a blast. It was really fun having to use every aspect of the combat system to its fullest--what weapon to use, which companions to bring, etc. I never had any desire to make ME2 any harder than that, but good on you for finding the best experience for yourself.

Insanity in this game is not that fun rather than other games where it was really a challenge and you had to know what you're doing. Even if you picked the best class, and brought the best team, your friendly AI sucks and more often than not, they'll die way too quickly for them to be any help

There's like two to five spots where Insanity really shows it's teeth, other than that it was a fun challenge.  
Horizon Turret Defense
Zaeed Plant (the room with the Mech, two gas tanks and infinite spawn)
Collector Ship Escape (one bit with one of those big guys, the name escapes me right now)
Maybe one section of Mordin's mission where you have lots of Krogan and little Cover
 
Short list of Insanity troubles:

• Endlessly spawning enemies always suck (Zaeed mission stands out as worst offender).
• Running out of Pistol Ammo before you have an alternative SMG is a fucking headache and a half as Adept.
  
• AI Squad spends most their time dead despite commands - you should almost always use Grunt and Thane/Garrus anyway. Grunt because he's hard to kill and Thane/Garrus has infinite sniper ammo.
  

Difficulty doesn't make the AI smarter, so its not a different game. Enemies have more HP and do more damage, more of them spawn, kind of standard.

Hardcore is perfect for me. Insanity is just overkill, personally.

" So you remember how you played Mass Effect 2 on Normal difficulty and you didn't care about any armor and weapon upgrades or you didn't have any motivation to mine the planets for minerals? Turns out that's just an odd balance choice from Bioware for this standard difficulty, where all the focus is on the story and not the combat.  
 
When you play the same game on the hardest Insanity difficulty you will face a completely different balance and it will feel like you are playing a completely different game. Essentially there are two games in one in Mass Effect 2. 
 
If you come to Insanity from Normal it will be quite brutal at first (at least for my 30-level soldier class it was), but that's when you are forced to learn the mechanics of the combat for the first time. And that's when you start to care about the upgrades of the armor and the weapons that the game has to offer (to get all of them you will want to mine as many planets as will be required). You also start to care about the team stats, I actually retrained my Shepard I think around 5 times until I found the combination that worked the best for my style of play.    The main focus of this other game that comes inside the same ME2 package is on combat and RPG elements, the combat is so challenging and satisfying that I can't stop playing the game although that's my second playthrough and I know the story and usually I would be doing this only to get the final achievements, but not this time. I have finished hiring everyone except Legion for my team now and I can't wait until this workday will be over and I will continue playing.  I haven't really had this kind of experience with any other game before.   Great job Bioware (and Christina Norman)!  "

I never played normal so it wasn't a HUGE upgrade in difficulty. The main thing for me was how brutal those big robots got, one of those things required a really well balanced team, and so those gave me some trouble.
The second big difference is how hard the final boss was until I realized that in that encounter harbinger drops heavy weapon ammo every time you smoke him, and you can just nuke the reaper a few times and he's done.

I just thought it was a bitch. Enemies soaked up bullets even with the strongest sniper rifle with warp bullets to the face. And with it being the second playthrough, I sure as hell didn't want to mine more. It lost its novelty in the first playthough. There were also parts that seem almost impossible. I was constantly searching for ammo. Enemies rushed your position. Like I said, a bitch.
 
The only games that I remember really enjoying on a higher difficulty were the original Halo and Jedi Outcast. They didn't just create bullet sponges. They added enemies. It's almost burned into my brain the number of flood that burst through the the ceiling on one of the later levels. That's how you do higher difficulty.

Playing ME2 on insanity was one of the best experiences I ever had while gaming. It might not be too difficult for some of you, but for me it was exactly right: not too frustrating, very rewarding. You become aware of your position, the powers and weapons you use and what your enemies are doing. It was indeed a whole new game for me.

Mass Effect 2 on insanity is probably my favourite gaming experience. I can't even describe the feeling of playing a Vanguard on insanity. You are dying and the only way of you getting your health and shield up again is by throwing yourself into battle again. I was so frustrated at times (like the first time you visit the collector ship), but man. At the end when you've killed you final enemy you sure feel like a bad ass motherskunker! 

" Mass Effect 2 on insanity is probably my favourite gaming experience. I can't even describe the feeling of playing a Vanguard on insanity. You are dying and the only way of you getting your health and shield up again is by throwing yourself into battle again. I was so frustrated at times (like the first time you visit the collector ship), but man. At the end when you've killed you final enemy you sure feel like a bad ass motherskunker!  "

Hmm, I didn't really find Insanity that hard. Just finished it a few minutes ago. It was still pretty fun, choke points in frustration only being the first encounter with the Collectors and aquiring the Reaper IFF. Everything else was a breeze. I used a level 30 Soldier, Heavy Warp ammo, Heavy Disruptor ammo and Inferno ammo as well as maxed out Adrenalin Rush. I cannot stress enough how crucial the last one is. Without it, you're completely screwed. Took me 14 hours total.
 
All in all, I wish they added a difficulty above Insanity. :p

Yeah, it was pretty good.

I agree 100% with the OP. My first time through I played the game on normal and while I enjoyed the combat I never really learned it all that well. On insanity though I had to pick team mates just for their abilities, pause the game a lot to give orders and so on. It's probably one of my favourite combat systems in any game, it's really well designed (combined with the enemy design). A lot of people said that ME2's combat was dumbed down but I found it much more strategic than ME1's. My only criticism would be that the boss battles aren't challenging in a fun way on Insanity, the way the rest of the combat is. Fighting the Praetorians, for example, isn't hard, it's just an extremely long battle of attrition. I can forgive them for that, but it's something they could definitely improve.

I found various parts difficult and others just annoying but only one particular part stands out til this very moment (I finished it in July-Aug 2010). The part where you investigate the Collector Ship, the very first part with the flying platforms. Harbinger shows up with some drones and 2 Scions. Man, with Harbinger's gung ho mentality (not to mention his Singularity-esque attack that disorients and sets Shepard back), the drones and Scions' Shockwave I was left frustrated with this part. I actually ended up rage quitting and didn't touch the game for a whole week but then I went back and finally beat it.

There are a couple of other spots I found tough like the two Praetorians you fight on Horizon and in the Collector Ship and Archangel's recruitment mission but that above bit was by far the toughest.

Here's a clip of it (this guy makes it look easy mainly because he has The Widow but believe me it IS on Insanity)

http://www.youtube.com/watch?v=UKRtNvpZr_Y

EDIT: Three more parts I found tough - Mordin's recruitment mission, turning on the valves. There are Vorchas shooting rockets from a ledge while Pyros and Krogan charge at you - fuck. The second one is getting the Reaper IFF, Husks and Abominations do quite some damage in big crowds but then you got Scions closing in too, just brutal. Last bit, Zaeed's loyalty. Big room, lots of cover but kind of boxed in at same time. Blue Suns mercs mostly Turians with shotguns, some pyros too and a big mech. Ugh, it took me a while it has to be said.

I played Insanity with a Vanguard. It was hard. very hard. But I appreciated the combat a lot more when I was done.

Insanity ruined my experience. I got up to horizon, the last encounter, and just thought 'fuck it', when my allies both died within 10 seconds because they didnt understand that staying in cover is a good behaviour.
 
I love Mass Effect, one of the best franchises of all time, for me, but Insanity is just a great chance to take something wonderful and make it nasty. I'm genuinely perplexed by those people who can say they breezed through it with only a handful of hiccups. Bravo!

" So you remember how you played Mass Effect 2 on Normal difficulty and you didn't care about any armor and weapon upgrades or you didn't have any motivation to mine the planets for minerals? Turns out that's just an odd balance choice from Bioware for this standard difficulty, where all the focus is on the story and not the combat."
 
Mm, really? I mean, I love it for the story, but I think combat in ME2 is what made me replay the game so many times. And the motivation for mining planets definitely increased once they released the patch vastly improving the mineral scanner. 
 
"When you play the same game on the hardest Insanity difficulty you will face a completely different balance and it will feel like you are playing a completely different game. Essentially there are two games in one in Mass Effect 2." I played my first time through on Hardcore and I got through most of it okay except for that floating platform fight. You all know the fight I'm talking about. The second time through though once you use the Geth Shield Boost you can survive just about anything, but you can't be careless either, especially on Insanity.
 
"If you come to Insanity from Normal it will be quite brutal at first (at least for my 30-level soldier class it was), but that's when you are forced to learn the mechanics of the combat for the first time."
Indeed! The combat in ME2 may not even seem that dynamic and interesting unless playing on the hardest difficulty level. On a lower setting, the skills behave more or less the same and you won't even realize how each one can give you a tactical advantage depending on your class and chosen squad. Granted, to some degree the skills overlap a bit anyway, but not as bad as they did in ME1. This time around it really does matter a bit more where you're spending your points. I found this to be especially true with power ammos. But a lot of other skills only work best anyway when an enemy is down to just their red health bar. But then if you're rushing to get enemies dispatched cause you're being swarmed, the finishing move on an enemy can really make a difference. Like when fighting the Collectors on their platforms. The instant their barriers are down, they get a concussive shot or throw. I prefer even to use squad members with this ability as they perform the action close to instantly than I can. So yeah, things really can make a difference and give you the advantage needed when carefully choosing skills. 
 
"And that's when you start to care about the upgrades of the armor and the weapons that the game has to offer (to get all of them you will want to mine as many planets as will be required). You also start to care about the team stats, I actually retrained my Shepard I think around 5 times until I found the combination that worked the best for my style of play."Always thought it was a shame you couldn't retrain your squad members too. But I guess it all helps to increase replayability. But yeah, upgrades matter. And if you're having a hard time earning cash, some weapon upgrades you may wish to skip. For example, I never use shotgun (I wish I did more ME2 cause shotguns are often my favorite kinds of weapons in games) or even assign it to my squad members cause I don't find it that effective with the exception of fighting Husks which are pretty manageable anyway.
 
"The main focus of this other game that comes inside the same ME2 package is on combat and RPG elements, the combat is so challenging and satisfying that I can't stop playing the game although that's my second playthrough and I know the story and usually I would be doing this only to get the final achievements, but not this time. I have finished hiring everyone except Legion for my team now and I can't wait until this workday will be over and I will continue playing.  I haven't really had this kind of experience with any other game before.   Great job Bioware (and Christina Norman)!  "Yeah ME2 is a good example of action that matters. What I mean by that, is you usually know exactly why you are fighting and what the objectives are and how accomplishing those objectives advances the story. This is kind of a problem I had in Halo: Reach. Love the game, but often times I didn't know why I was fighting toward something. I seriously thought I'd understand it better just by turning on subtitles which I usually do in games anyway, but the subtitles only seemed to work during cutscenes. So I understood sometimes why I was fighting my way through hundreds of Covenant, but other times I was like....what am I doing here anyway?  I realize Halo is a much different game, but anyway.
 
But in ME2, being that it's such a strong RPG anyway, you're rarely just shooting people for the hell of it. At least it doesn't feel that way. And you usually know precisely what you're in a place to do. The sidequests don't always brief you of what's going on, but sometimes you gotta figure it out as you go along too. Anyway, glad you're enjoying the game on Insanity. Seriously, Geth Shield Boost!
 
Not sure I did this quote right. It's my first post and I'm not used to this particular forum software.