Great game. Fantastic multiplayer.
The multiplayer has so many guns, perks, killstreaks, weapon camo, achievements... There's so much to offer you just can't get bored. The online maps are fantastic, some of my favourite in the Modern Warfare series are on this game.
Special Ops is a great extra set of missions which lets you try lots of different play styles and throws you into all kinds of situations. Definitely kept on your toes.
Slight problem with hacking/boosting on multiplayer and where it's not the latest call of duty game it hasn't been properly patched. Doesn't effect very much, you can tell when you join an online game you're better off leaving.