Check out this installation done by Diversified Technologies, which combines an Xbox 360, Windows XP PC and a high definition video switcher
and distribution system to play music, movies and pictures throughout the house. Although they are not streaming video
from the PC because it isn't running Media Center, the Zektor video switch and Audio Authority distribution system
display content from the 360 or satellite source to any of the connected TV's.
Thats certainly an interesting approach, however one has to wonder about all the heat the 360 puts out, not to mention whether it has space for the hard drive on the side in that slot. That aside, the 360's smooth interface and wireless controllers make it ideal for this sort of application, I guess we'll see these showing up on the HD Beat flickr group soon.