The single player aspect of this game is without a doubt the least bit challenging. Playing the game on hard is a must... and even then it is far too easy. On no game, on the hardest difficulty should you be able to run up to someone who's shooting at you and stab them in the face. The story is alright, however lacks any real substance and relatively uninspired.
Multiplayer- I'm not sure if this of true for everyone however the lag is absolutely abysmal. On countless occasions I have encountered getting killed 2/3 seconds after getting behind cover, and the lag reversing what my character was doing e.g. crouching or shooting a bolt action rifle 3 times in about the space of a second. Also having 8 maps total (for different game types) is a joke.
Graphics- at times the game can look amazing, at others it looks grainy and poor.
My advice, wait for black ops.