"MythTV itself might qualify in this category. However, I find
Myth makes a good OS (mythbuntu) and PVR (with a great web
interface), but I think it is fairly awful at organizing your media
and playing web vids. So, I leave it out of the media center
category. I personally run a Mythbuntu system with the following
three media centers installed on top of MythTV to organize my local
media and watch web content.
"This media center was designed for the original XBox hardware.
However, it has since been ported to Linux, Apple and Windows (and
other game systems). It has an extremely beautiful interface. XBMC
indexes the music and videos on your hard drive or networked drives
and plays them back with a lot of elegance. It is easy to configure
your remote control and video playback utilizes VDPAU on nvidia
cards. So, you get amazing performance during playback (HD video
uses less than 10% of your CPU)."