G4TV show X-Play have released a short preview featuring Chet Faliszek who talks about the upcoming Left 4 Dead. He describes the game as a "four-player survival co-op" rather than as a FPS and comments on the level design.
Left 4 Dead will feature four levels whicn you and your buddies need to work through per map with a safe point in between these levels. At the end of these four stages there will be a final stage where you're holed up and need to survive an infected onslaught. I'm not sure if Chet was referring to just the Cornfield map (which was shown here) or to all maps. I think it's a pretty cool set up, especially final stage.
Interestingly there was a shot of an infected trying to break down a door. This is a great feature if it means doors (and hopefully other barricades) will slow and not stop entirely the foe.
Enjoy the video. Thanks
G4TV
Watch the video.