I have a a few HTPCs running XBMC spread around the house and I'm quite happy with the setup, though it's mainly acting as a movie server/client arrangement similar to a poor man's Kaleidescape. I would love to convince my wife to ditch Cable TV and TiVo (combined around $70/month) in favor of a streaming solution. XBMC will currently recognize my PlayOn server, but XBMC really needs to refine their DLNA/uPnP implementation in regards to stability.

The Boxee Box in combination with either PlayOn (I already have a basic license from before they went to the subscription model) and/or Hulu Plus and Netflix (also already a member on a 2-disc plan) would drop that down by $62-$70 month. The movie and pre-recorded/downloaded TV interface isn't quite as pretty as XBMC, but it still aggregates meta data well enough to be passable.

Boxee is supposedly in talks to license the software to other CE manufacturers, so my ideal solution would be the current Boxee Box software and interface bundled into a Blu-Ray player. This would allow a single source device to provide all of my content at each TV. LG has also recently signed an agreement with Plex (another XBMC fork similar to Boxee, but more Mac-centric), so that might make it to market before a similar Boxee based solution.