Plex http://plexapp.com is based on an earlier version of XBMC. They have it running on iPhone, iPad and someone hacked it onto the Apple TV and did a similar video a few months ago: http://www.vimeo.com/16479085
I'd put my money on plex as an easier way to manage content and stream it from a box elsewhere in the house.
(I have plex running on a 2009 Mac Mini and it works really well)
Plex is incredibly awesome. My whole house runs on it. Unfortunately it transcodes all video on ATV2 from another computer running the server. This XMBC app decodes the videos on the ATV2 itself - which is awesome, and I hope the Plex crew gets that up and running as well.
I'd put my money on plex as an easier way to manage content and stream it from a box elsewhere in the house.
(I have plex running on a 2009 Mac Mini and it works really well)