Impressions on Realistic difficulty:

-Interrogation scene is really really cool. Still dunno why a big criminal lord went out and killed my no-name daughter though.

-Mark and Execute is just as lame as I thought it'd be.

-Cover system's the same as the one in R6 Vegas, which I loved. Great addition. Shifting automatically towards cover seems to be the kind used in Wanted and Terminator Salvation, which is fine.

-Normal shooting feels quite good.

-Graphics look nice and modern. You'd never know this was an Unreal 2.5 engine. The AA isn't enough to hide the jaggies though.

-Sonar goggles: No idea what they're for. In other Splinter Cells, I almost always had my NVGs on. In this game, I probably won't use them at all, unless it's some special area they concoct.

-Controls feel a little weird, because of the rejiggering they did to fit in cover and other options. Aiming is now relegated to clicking the right analog stick, which doesn't feel quite as smooth as holding LT, what you usually do in other games. Also, crouch is now left bumper, instead of clicking the left analog stick. Reloading is now clicking left analog stick, which is gonna take a LOT of getting used to. I'm used to reloading with the X button, which is now for using grenades. So... yea, I just threw a fucking frag grenade at my feet when I meant to reload my pistol.

-I'm not sure if removing the light meter was a good idea. Once you're in darkness, it all turns black and white and it becomes somewhat uncertain exactly where the shadows are.

-The pistol HAS INFINITE AMMO. Even on Realistic. WTF?

At the end of the day, they do make you feel like a powerful badass, which is cool. And honestly, there's no need for Mark and Execute, given how easy it is to simply gun down the enemies with normal shots. I dunno about a panther, but it's a nice feeling to take down a roomful of guys who are all shouting "Hold position" over and over again. Definitely a day one purchase for me. 
 
There's something very visceral and tense when you just barely miss a guy's head on your first shot, because their head jerks back from alarm, and you've gotta quickly try and snap off a second shot while they're still stunned. It's a really good feeling when you get that kill on the second shot. Because you saved it from going bad, even though you missed on the first attempt. It's a quick jolt of tension and release that feels satisfying.

Also... has anyone noticed that the soldiers will sometimes grab their head when you make a headshot? Kinda the same phenomenon as in Arkham Asylum. Except here, it makes even less sense. I don't think any of the previous SCs had that happen. When you made a headshot, their body just dropped like a stone. Not sure a human body would be capable of clutching their head when the brain matter's just been evaluated.
 
You know that big warehouse room with the hanging generator experiment thingy? Right at ground level near the beginning of the demo? I actually went up the shaft and sat on the ledge and tried to gun everyone down. Just to see what would happen. There were about 5 or 6 soldiers in that room, I think. Anyways, I think the health system might be a bit generous, even on Realistic, because I just sat on that ledge and shot everyone down while they pelted me with rounds. Maybe the ledge provided me with a bit of cover, I dunno. 
 
One thing I really like, and is a big improvement over the other SCs: the enemy reactions. In the previous entries, you did something and would hear a lot of:

"Who's there?"
"Who turned out the light?"
"Did I hear something?"
"Am I seeing things?"

As opposed to this game, where you hear a lot of "Motherfucker!"s and "Holy shit!"s. Very realistic reactions. 
 
The Five seveN seems godly. I don't know why there's even an option for a secondary weapon, there's never a need for it. With the pistol, you've got 20 rounds + infinite ammo and a silencer for stealth. Accuracy's quite good as well. Maybe later you get a silenced sniper rifle for long distance shooting and it'll be useful, but right now, the pistol's the best option for everything. MP5Ns and M468s deliver more firepower, but since enemies take 2-3 body shots before going down, it's not really a noticeable advantage. If there was an option to mount a silencer to them, I might use them. *shrug*
 
LOL... wtf? I just redid that room but had Sam shooting while hanging onto the window ledge. And I killed almost everyone. Without exposing any part of my body, I could zoom in and accurately place body shots on all the enemies in the room, except for one guy off in the side room. Which I shot at range and earned a Mark and Execute for.

Wow.

The game just seems amazingly easy.

Impressions on Realistic difficulty:

-Interrogation scene is really really cool. Still dunno why a big criminal lord went out and killed my no-name daughter though.

-Mark and Execute is just as lame as I thought it'd be.

-Cover system's the same as the one in R6 Vegas, which I loved. Great addition. Shifting automatically towards cover seems to be the kind used in Wanted and Terminator Salvation, which is fine.

-Normal shooting feels quite good.

-Graphics look nice and modern. You'd never know this was an Unreal 2.5 engine. The AA isn't enough to hide the jaggies though.

-Sonar goggles: No idea what they're for. In other Splinter Cells, I almost always had my NVGs on. In this game, I probably won't use them at all, unless it's some special area they concoct.

-Controls feel a little weird, because of the rejiggering they did to fit in cover and other options. Aiming is now relegated to clicking the right analog stick, which doesn't feel quite as smooth as holding LT, what you usually do in other games. Also, crouch is now left bumper, instead of clicking the left analog stick. Reloading is now clicking left analog stick, which is gonna take a LOT of getting used to. I'm used to reloading with the X button, which is now for using grenades. So... yea, I just threw a fucking frag grenade at my feet when I meant to reload my pistol.

-I'm not sure if removing the light meter was a good idea. Once you're in darkness, it all turns black and white and it becomes somewhat uncertain exactly where the shadows are.

-The pistol HAS INFINITE AMMO. Even on Realistic. WTF?

At the end of the day, they do make you feel like a powerful badass, which is cool. And honestly, there's no need for Mark and Execute, given how easy it is to simply gun down the enemies with normal shots. I dunno about a panther, but it's a nice feeling to take down a roomful of guys who are all shouting "Hold position" over and over again. Definitely a day one purchase for me. 
 
There's something very visceral and tense when you just barely miss a guy's head on your first shot, because their head jerks back from alarm, and you've gotta quickly try and snap off a second shot while they're still stunned. It's a really good feeling when you get that kill on the second shot. Because you saved it from going bad, even though you missed on the first attempt. It's a quick jolt of tension and release that feels satisfying.

Also... has anyone noticed that the soldiers will sometimes grab their head when you make a headshot? Kinda the same phenomenon as in Arkham Asylum. Except here, it makes even less sense. I don't think any of the previous SCs had that happen. When you made a headshot, their body just dropped like a stone. Not sure a human body would be capable of clutching their head when the brain matter's just been evaluated.
 
You know that big warehouse room with the hanging generator experiment thingy? Right at ground level near the beginning of the demo? I actually went up the shaft and sat on the ledge and tried to gun everyone down. Just to see what would happen. There were about 5 or 6 soldiers in that room, I think. Anyways, I think the health system might be a bit generous, even on Realistic, because I just sat on that ledge and shot everyone down while they pelted me with rounds. Maybe the ledge provided me with a bit of cover, I dunno. 
 
One thing I really like, and is a big improvement over the other SCs: the enemy reactions. In the previous entries, you did something and would hear a lot of:

"Who's there?"
"Who turned out the light?"
"Did I hear something?"
"Am I seeing things?"

As opposed to this game, where you hear a lot of "Motherfucker!"s and "Holy shit!"s. Very realistic reactions. 
 
The Five seveN seems godly. I don't know why there's even an option for a secondary weapon, there's never a need for it. With the pistol, you've got 20 rounds + infinite ammo and a silencer for stealth. Accuracy's quite good as well. Maybe later you get a silenced sniper rifle for long distance shooting and it'll be useful, but right now, the pistol's the best option for everything. MP5Ns and M468s deliver more firepower, but since enemies take 2-3 body shots before going down, it's not really a noticeable advantage. If there was an option to mount a silencer to them, I might use them. *shrug*
 
LOL... wtf? I just redid that room but had Sam shooting while hanging onto the window ledge. And I killed almost everyone. Without exposing any part of my body, I could zoom in and accurately place body shots on all the enemies in the room, except for one guy off in the side room. Which I shot at range and earned a Mark and Execute for.

Wow.

The game just seems amazingly easy.