..Aside from the pop-up and buggy spawning of enemies and their glitchy animations.
Its kind of boring at times; lots of context sensitive button promts and whatnot.. The campaign is more a display of "look at what we can do with particle effects and lighting" than it is a compelling story or series of memorable moments.
Minor gripes about the singleplayer are no big deal considering how good the multiplayer portion is--thats where the real bread and butter is at.