played it a bit with others who weren't too great. One neat thing is that the level seemed very open and confusing (which would be nice for Versus). We didn't finish, I'll play more tomorrow.
and I put on triple-buffering since I just noticed L4D supports it native, but there seems to be a weird lag when using it. I've been using D3Doverrider to triple-buffer all my games and there was nothing when when using that.