The new media management features in the upcoming Plex/Nine release look great: http://vimeo.com/11880867
The Apple Bluetooth keyboard is small enough to be living room friendly.
Overall, a Mac mini isn't quite as simple as AppleTV, but it's far more functional.
If a boxee box does the job for $200, has 1080p, 7.1 out, 802.11n / Gig.E why bother spending $600?
I hope the Logitech setup GoogleTv box does the job.
It's always on, so it's a great home storage server (I have a Drobo w/ 4.5TB of storage attached via FireWire 800).
It downloads torrents & podcasts nicely.
Also, the shared library support coming in Plex/Nine looks killer. I'm looking forward to running Plex on my MacBook without having to maintain a separate metadata library.