Gamepro.com is going nuts with the XBox Doom 3 stuff, as their latest feature is an interview with Vicarious Visions, the company behind the XBox port of Doom 3. The interview talks about a bunch of stuff related to the console version:
KB: Our biggest addition for the Xbox is the ability to play the single player game with a friend in co-op mode. We’re also modifying and balancing combat and demon behaviours to present challenging, but not frustrating encounters while still maintaining the action, intensity and terror of Doom 3. There’s a ton of work going into the balance and pacing of the game as well as the control mechanisms -– the player needs to feel connected with the game and a part of the environment in order to suspend their disbelief and really draw them into the atmosphere and terror of the game. We also draw players in with true Dolby 5.1 surround sound support -– there’s nothing scarier than hearing a Demon sneaking up from behind you.
So I guess that confirms no co-op on the PC. Oh well.