Relic stated that the switch to Steamworks will allow them to do things for Retribution like "guest passes, free multiplayer weekends, pre-loading and the ability to provide fast turn-around on future patches and updates." Unfortunately Steamworks support won't be added to the original game or Chaos Rising nor will the content in Retribution be added to those to games when Retribution is released in the first quarter of 2011. The good news is that owners of the original game and Chaos Rising will be able to participate in a multiplayer beta of Retribution via Steam sometime in 2011.
This is the latest game franchise to dump Games For Windows Live for Steam. Bethesda Softworks announced earlier this year that Fallout: New Vegas would use Steamworks after using Games For Windows Live for Fallout 3 and Square Enix used Steamworks for Kane and Lynch 2 after using Games For Windows Live for the original game.
Download HD Dawn of War II: Retribution Announcement Trailer (165 MB)