The game is superb on many levels. Cinematically the single player Campaign is unequaled by other First Person Shooters even on the PC. The graphics are gorgeous, sounds and atmosphere are also spot on. Overall it's short, you can replay it on harder difficulties but if you will never use the multiplayer content of this game the asking price is very high for what you would get.
The 2 player extra missions are superb fun to do with a friends, I really recommend you grab a friend and do them after the campaign.
Multiplayer is great for jump in and play fun. If you have played a multiplayer FPS on a console it's exactly like that, the system automatically matches a suitable game for you based on the type you choose and finds the best host and so far this has resulted in me experiencing a laggy game only once, some people complain of lag more but I'm not sure if that's just cause they got killed
In comparison to MW1 the difference in multiplayer isn't phenomenal but there is a lot of new stuff. New perk system, customisable kill streak bonuses and ways to customise your class with favourite items and specials. There is deffinately a lot more ways to die where you pretty much have no opportunity to avoid though such as Predator missiles, C130s etc. Hell of a lot of fun when you get them but not so much when you get killed by them!
Just a shame Left 4 Dead 2 has come out pretty much the same time, not sure how much CoD will get played in my group of friends now