http://www.xbmc.org
I'm hearing good things so far from this release. Add-ons are not such a PITA and you can install them directly from XBMC. This is the one thing that Boxee had over XBMC, but it the add-ons are easy to install, then I'm going back to XBMC.
I'm also going to experiment a little and try out the XBMC Live edition on a USB drive. Anyone else using XBMC Live?