The most fun will come from playing with friends. I don't know any more about the game than what has been shown to me...it could end up sucking. But I know these guys make good multiplayer games, and the best part of Left 4 Dead is the integration of the multiplayer features.
I say give it a shot while playing online, that's where the excitement and fun will be, and that's what makes it totally different from your average FPS.
LEFT4DEAD411.COM
Bet with disolitude: Left4Dead will have a higher Metacritic rating than Project Origin, 3 months after the second game's release. (hasn't been 3 months but it looks like I won :-p )