This video on On10.net shows Steve Lindsay from Microsoft showing this Media Center system. He shows off Webguide, his 4 tuner system, Windows Home Server and a custom application for streaming DivX files.
What I like about the video is it shows the real possibilities of Media Center using existing components and some ingenuity.
http://on10.net/Blogs/Brianjo/amazing-media-center-setup/
Steve has started a blog on Media Center too
http://on10.net/Blogs/EnglishBloke/time-to-introduce-myself/