I don' t think this is very relevant though. How many of all those 360 buyers will use an OS on their console? Dreamcast also had a Linux version already but I guess most gamers mainly stick to using their consoles for playing games.
That was a long time ago, before mass downloading of media, and before many peoples TV' s supported HD output.
Today, lots of people have television shows, movies, music, clips of assorted things, programs, and countless other things on their computers that they would like to be able to easily view on their living room TV sets.
Linux allows people to do this. I personally believe having the ability to remotely access files from your pc through your living room console is extremely useful. Hence the reason MS has gone and added this feature to Vista and the Xbox360. Now, tons of you love what MS does, and they just did this, so don' t tell me its not a very useful feature, because MS obviously thought it was, enough to advertise about it on every page that they advertise Vista.