I've been playing around with Boxee
this past week after their latest alpha and I'm _really_ impressed. This is what I've been looking for for a few years now. I can, using my Mac Mini, pretty much unplug the keyboard and _greatly_ reduce the mouse usage.
My goal home theater PC scenario has always been:
1) download favorite TV shows automatically with BitTorrent
2) watch ripped DVDs
3) listen to iTunes songs
4) access YouTube and other web video content online
5) do all this with remote control
6) look "professional" (rename clunky download names, download cover art)
Boxee ticks all the above boxes. I am still using Vuze for downloads (running in the background with AzSMRC to control it from my laptop) but it dumps into my video folder where Boxee picks up the newly downloaded files.
I tried this with a PC for the past few years and it was never good enough to remove the feel of Windows - traversing directories and switching between players. I upgraded to a Mac Mini last year and was semi-happy using Nice Player and iTunes to watch shows and downloads. Still required a mouse to interact with OS X.
Drawbacks include no DVR support (doesn't matter to me since I don't have a cable box or satellite) and typical bugs in the alpha (mis-identifying songs/videos, occasional crashes or sluggishness, UI inconsistencies).
Happy to send invites to anyone that PMs as I believe it's still invite-only. Excited to see where they take this.