[kupoartist]

As far as I know, Doom has a "when it's done" release date, largely because it has missed release dates in the past, and they don't want too miss to many more (Duke Nukem Forever did the same. People are still waiting for it!). Any release date you see is likely to be pure speculation - some believe they'll see it in the Summer, some later. I'm not sure if it'll be a simultaneous PC / XBox release, the only thing I'd say is that its unlikely that the XBox version will see a release before the PC version.

Multiplayer Co-op will be limited to Live, so no bundling into the same room to play split screen like for Halo... also, beyond co-op, I understand that there will be nothing beyond Deathmatch - and classic 4 player DOOM deathmatch at that. The XBox version falls behind the PC version there, because chances are that someone will mod 5+ player battles and maps into the PC version. If the game is good enough to bother modding...

Chances are, any important announcements on Doom III will be made at E3, perhaps they'll give us a concrete release date, though it pretty likely that there'll be a nice shiny new video released... You may want to check out last year's movies: https://www.fileplanet.com/section.aspx?s=31875 (or search for them at a non-registration site... good luck with that though). Personally, I thought that last year's video was atmospheric and graphically cool... but some of those Monster Designs just look... crap.