PLUCKYMCE:I was waiting on this forever. Finally gave up and went to Sonos.
The Sonos is a killer product. I just wish an enterprizing individual would capitalize on M$'s lack of attention to mutlizone audio. Our MCE machines are powerfull enough for multiple HiDef streams, playback and recording, however a simple mutlizone app is missing. We've made the commitment to MCE and it is silly to buy another product to do something our machines and extenders could do without breaking a sweat.
If it were cost effective I would look to the Niveus, Exceptional Innovation, or other multizone playback options. Unfotunately they cost thousands of dollars and typically require a new MCE purchase.
I've considered the Sonos, but it baffles me that someone has not created a Sonos like remote and solution for MCE/Extender mutlizone playback.