I wouldn't touch an AppleTV myself, either, but I didn't know it ran Boxee and XBMC at an unacceptable level of performance. On top of the processor, the Nvidia chip on it isn't that powerful either. I'm not sure about the replacement software, but Apple's own isn't able to output anything higher than 720p.

Boxee looks to be releasing their own hardware, so that's something to keep an eye on next month for anyone interested in a media playback device with a decent UI (announcement December 7th).

So far the Nvidia ION platform has been a complete disappointment in pricing. No one that I know of has released anything built with it in an ultra-small package at a decent price ($200 for instance), even without software. That means it's difficult to make one of those low-cost, low-power and completely silent MythTV front-ends right now.