-Death streaks (why should you be rewarded for dying?)
-Kill streak rewards (UAV, chopper, airstrike, cool. Some of them get completely ridiculous like the AC130. This doesn't add to gameplay IMO.)
-No dedicated servers. Really IW?
-Camping. This is more of a problem with the players themselves, but it feels like the maps encourage it. May not be much of a problem in regular mode, but it shouldn't take more than 3 shots from a 7.62 to kill somebody.
This is just my opinion of the game. I know most people won't agree with me, but I'm not trying to bash anyone.