Simply amazing game.
Single player modes story is very simple, you play in modern times, the good guys(US or British) and try to prevent the bad guys from being...bad. Obviously the story is better than that and there are some nice moments to be had there but to tell you the truth I was so excited by the multiplayer action that the single player really took a back seat for me atleast.
The multiplayer part of this game is just great. There are some nice maps to be seen, great weapons, and a healthy dose of modes to choose from with ways to make the game harder or easier, more simulation like or arcade like. The multiplayer also has a fine rank system where you earn experience points that help you move up in rank and unlock some stuff on the game. All of this helps to add a ton of replay value to the game.
With great graphics and terrific sound design added to everything else I have stated, I see no reason why you won't be just as addicted to this game as I am.