From IGN.
Four player co-op!
Forget the news about the big three press conferences; forget anything you've heard about frame rate. While you are at it, forget about Halo 3. From now until the game is actually in my hands, the only thing we care about is Gears of War. While sitting in on a 20 minute presentation from Epic my excitement over Microsoft's new console jumped back up to a near fan-boy level. Furthermore, this demonstration only confirmed what we already felt about this game, Gears of War is the killer app on Xbox 360.
Four player co-op!
Gears of War allows up to four players to enjoy the campaign mode co-operatively.