Well the playstyles are still there - so if you did enjoy AvP2 then you can at least look forward to more of the same:
Marine: Running about with your heartbeat thumping, shooting any dark corner because sooner or later something will be hiding in one.
Alien: Stalking around on ceilings and in dark places, striking when least expected.
Pred: Similar but with a cloaking device and some more high-tech weaponry.
Graphically it's definitely better, but that's expected. The demo doesn't really give any indication of how the single player will be, it's multiplayer only and death match at that - so not best suited to give a good idea.
I'm getting the full thing based on game-play alone, I love the atmosphere and world setting.