Oh - it's Left 4 Dead 2 from valve...
There was a pretty big following here when the 1st one came out and Valve has made a lot of controvertial changes to the sequel (including getting the sequel in out leass than a year after).
Left 4 Dead (the original) is a blast and has taken more of my game time than anything - probably since Battlefield 2.
The demo is only available until next monday I think so anyone who wants to check it out should go ahead and get a taste!
Good Stuff, Maynard!