I agree with the others, it would have been nice to have a single player demo instead of multiplayer. I still buy a game for the single player campaign first and foremost. You can't really get a feel for what single player is going to be like from a multiplayer demo.
I can say though that Crysis 2 has been a lot of fun to play. I bought the game yesterday when it released and I am really enjoying it. You can tell to some degree that it has been influenced by being developed on consoles, but the game is still really fun to play and it looks amazing maxed out. Unfortunately (for some) it doesn't run on DX11. It would have been nice to see what DX11 is all about on a Crysis game, but for now we are stuck at DX9 only. There is a rumored DX11 patch due to come out sometime though. Who knows if that will really happen or not.
If you are on the fence about getting this game, know that it is a lot of fun to play. It isn't exactly like the first crysis, but it is still a ton of fun. You will have to decide if it is worth it at retail price right now. For me, it was.