The single player campaign could've been longer, but going back and playing levels again doesn't get old.
I'm really not a huge online multiplayer guy, mainly because I get whooped in everything against actual people, but I cannot say that I don't like this game's online multiplayer. The only things that could've been better is, 1) the fact that you can't get up against a wall, 2) when you die you always seem to have to cross the entire map to find any action, and 3) the AI enemies seem much harder in multiplayer than single player.
This game is definitely going to be one of my favorite games that I have for a long time, and I doubt that I'll ever stop playing it for long periods at a time. All in all, if you like endless action that looks, sounds, and feels absolutely amazing, then this game is exactly what you need.