You may remember we posted an open letter from Marc Whitten, General Manager of Xbox LIVE, just after Xmas which promised to thank LIVE members with a free XBLA game after the problems Xbox Live experience over the Xmas period.

Well, that game has today been revealed as Unreal engine-powered shooter Undertow, and it will be available free of charge from 10am GMT on Wednesday January 23 until 8am GMT on Monday January 28. It’s normally priced at 800 MS Points.
 
More details from GamerScore Blog:

"Recently, Xbox.com posted a letter from Marc Whitten, General Manager of Xbox LIVE, thanking subscribers for their patience with the service. We’ve implemented several improvements to the service, to help ensure ongoing reliability and performance.  As the popularity of Xbox LIVE expands, we’ll continue to closely monitor the service and make adjustments.  As always, if you are having any problems, please contact your local support (1-800-4-MYXBOX in North America) so that we can assist you. 
 
Marc announced that all Xbox LIVE members around the world would have access to a full Xbox LIVE Arcade game to download free of charge. We’re pleased to announce that beginning next Wednesday, 2:00 a.m. PST through Sunday, 11:59 p.m. PST, Xbox LIVE members worldwide can download the full version of the recent award-winning Xbox LIVE Arcade game, Undertow."