First off, I am a huge Halo fan. I have been looking forward to this for a long time. My copy came on the 13th, a day before launch. I played through the SP, and it was great, but not Halo great to me. I finished, and I was happy I finished. Any more FPS Halo and I do not think I could take it. There where a few annoying, bugs, mainly my teamates getting stuck and not teleporting to me for a good long bit. There where a few level design issues I found making it very hard for myself to complete the objective. In these situations I found myself jumping around behind, sprinting past the enemies, completeing the objective and causing a cutscene.  Make no mistake, I loved this. This sure was some Halo ass Halo! 
 
The ending was not as good as I expected. In Halo 3, the craaazzzy, frantic warthog escape was one of my favourite endings to a game. This game seemed a bit less intense. I very much enjoy the endings addition to the lore however.
 

Not good enough. Read the books again :).

Should really have said - So what about you few who have finished it. Did you find it had a few issues. Did you find you did not get that same Halo Buzz from the game/ending?

" Just blasted through the prequel novel before I played the game.  Can anyone tell me if I will spot anything in the game relating to the book?  No spoilers if you can, just tell me you can't say anything about it if avoiding spoilers is impossible. "

" Not good enough. Read the books again :). "

What difficulty was it on? Because Heoric or Legendary are the only right ways to play through it.

" @mattjam3000: I really, really dug the ending (the bit after the credits especially) and it was kind of awesome how it dovetailed into the beginning of the first game. As for the game in general I'd agree that there was quite a lot of stuff that annoyed me as I was playing through it, but yeah overall I liked it well enough. "

" What difficulty was it on? Because Heoric or Legendary are the only right ways to play through it. "

I do think the Spartan AI seems a little weak still. I understand how your team would be overpowered with a bunch of suped-up Spartans, but still. The part you mentioned with the turrets and such, just a lot of legwork for one player.  
 
Also, during the space battle, there was one point where the Orbital Defense system was absolutely laying into one of the Phantoms. Seriously all the Orbital Defense system's guns were landing hundreds of shots on the Phantom, but it wasn't until I swooped around and attacked it that it actually blew up. Sort of goofy.  

Im going to hit up another issue I had with the ending, so stop now if you still havent got the spoiler idea. The MAC gun at the end was all wrong. The MAC gun is a huge, primary ship weapon that fires one huge shell, and takes a long long time to recharge. Reach did have better MAC guns, but they where orbital, there are no MAC guns acting like anti air guns on the ground but oh well they have to make the game fun I suppose! I also agree that it had a  almost darker tone and maybe didnt need that jacked up ending that the other games have. I just like a huge WOW kick at the end of my Halo Games. I finish the game and go HOLEY SHIT. I did not get that and that is why im slightly dis-satisied.

Read the books backwards to be a true halo fan. Halo mysteries will reveal themselves to you.

I haven't played the game, but I have seen major bits of it including the ending, and I have to say that the ending to Reach gave me a "wow" moment so strong it made me want to buy the game when I've had little to no interest in it otherwise. While the actual final "boss" isn't anything spectacular, it's what happens after the credits that had a big emotional impact (on me, at least). Been dying to talk about it ever since, but I don't want to spoil it for anyone since most people either don't have the game yet or are just picking it up now. 
 
Bungie's sendoff words also made me tear up. I'm not some die-hard Halo fan by any means, but I still recognize it's the end of an era.

" I haven't played the game, but I have seen major bits of it including the ending, and I have to say that the ending to Reach gave me a "wow" moment so strong it made me want to buy the game when I've had little to no interest in it otherwise. While the actual final "boss" isn't anything spectacular, it's what happens after the credits that had a big emotional impact (on me, at least). "

" @Hailinel: I don't even remember what the last boss of Halo 3 was; that's how much I cared about that game. Not that I actively hated it or anything, but I finished it an put it away in the collection without much thought.  "

What's with everyone talking about playing the game? Doesn't it come out tomorrow?

" What's with everyone talking about playing the game? Doesn't it come out tomorrow? "

" What's with everyone talking about playing the game? Doesn't it come out tomorrow? "

 I thought the intro to the Covenant was really disappointing. I mean, a little skirmish for some unimportant settlement? I was hoping first contact between Human and Covenant would be epic and unforgettable. And so I learn that this is not the first contact, it was just a planet we lost...geez there are thousands of planets. 
 
But somewhere in there, maybe 2/3 of the way thru, I really felt akin to the setting and could well imagine that one day far into the future, humanity would be fighting for its survival against an alien race in an interstellar war.
 

If you're unfamiliar with the lore by the time of the Fall of Reach (2552) the Humans and Covenant had been slugging it out for twenty-seven years. Reach was the final major Human colony outside of Earth. Almost all of the others had been "glassed" from orbit. So, the appearance of a Covenant strike force wouldn't be horribly shocking to anyone. There was at least an entire generation of Humans who had grown up with the Covenant assaulting Humanity and Humanity resoundingly losing. The real shock was supposed to be the recon mission where you and Jun discover that this isn't a Covenant raid but a full blown planetary invasion. The UNSC knew the Covenant was going to come eventually as shown by them having the "Winter Contingency" available for just that occurrence. This is definitely the low low point of Humanity because the Covenant are pouring across Human controlled space destroying everything in their path with impunity. 
 
So, I think Bungie did a great job capturing that hopeless feeling that no matter how many Covenant troops, ships, and supplies are destroyed we are going to lose and everyone is going to die. It also feels much more pure because this is a game that's just about straight up military conflict. No Flood, no Forerunner mysticism, no Prophets spouting religious propoganda. This is Covenant and Human troops messing one another up on a planetary scale.
 
Also, if you now go back and play the Halo games in their chronological order (Halo Wars, Halo Reach, Halo, Halo 2, Halo 3: ODST, and Halo 3) you'll get that "trilogy" feeling of initial conflict, middle point hopelessness, and rise to eventually victory against all odds.
 
It also just helps to point out how incredible Master Chief is that he was able to almost single-handedly bring the Covenant to its knees.

man i thought i as one of the few to finish the game today

Ive read all the books and had a few... issues with the story. Things like how Halsey knew about the spartan III's, the non-existant massive space battle above and how noble 6 managed to survive falling back to reach from space with mark V armour and no parachute!