My major annoyance so far is not being able to aim your weapon when you are running. Every other FPS i\'ve ever played allows you to strafe, run sideways, backwards while running. And while this is not "realistic" this is a video game, not real life. It just makes running "forrest gump" style feel clunky.
I only have about 3 hours of time with the game so far, but it already has wowed me more than MW2 ever did my first few weeks of playing. If I could stand playing FPS games with a controller I would have got it for the 360, but I can\'t give up the KB/M.