I just got this press release from Activision:

Turn back the clocks and crank-up the action, id Software’s DOOM® is available now for the Xbox 360™ video game and entertainment system by download from Microsoft’s Xbox Live® Arcade. The game, which premiered today at X06 in Barcelona, brings legendary DOOM mayhem to gamers, who for the first time ever can relive the classic demon-blasting fragfest in both single-player and 2-4-player co-operative and Deathmatch modes over Xbox Live or splitscreen. DOOM for Xbox Live Arcade is available in most worldwide markets for 800 points and is rated “M” for Mature by the ESRB.

I'm actually kind of excited about Deathmatch over Xbox Live!