Skreczi, Resil and I tried the demo a few days ago. If it wasn't for the lag (which was unbearable on the second level) we'd buy the game in a heartbeat. For now we're waiting for some official info saying "there's no more lag in L4D". Maybe there were only a few overworked servers for the demo, I dunno, but warping zombies kinda steal the fun from a game like this. ;)