I also had asked about whether Sonos would work with uPNP (specifically with MC) for a friend of mine who was looking at the Sonos.
Here is what they said:
"Sonos does utilize UPnP, but accesses files over the network thru file sharing (CIFS or SMB). Having a media center program that supports UPNP isn't necessary in order for Sonos to access your library."
I then fired another question at them, and was a little more descriptive in what I was trying to find out, and they said:
"A note from one of my tech support people:
'No, he can't use his existing Media Center software to act as a UPnP Server in the sense that it will stream files to Sonos. Sonos will access his files over the network via file sharing, thus requiring 1 ZP to be hardwired. The hardwired ZP isn't a "server", every ZP is the same, but if there is only 1 hardwired ZP it will be the only ZP accessing files off the PC."
So, I told my friend, forget about the Sonos for noew (and probably forever). Here in Australia, it would cost my friend about $2500 for a wireless remote unit, and two Sonos stations.
It would be cheaper to buy two basic laptops with wireless, a license for MC 11, a license for Netremote, and a pocketPC. Then he could get assistance setting iot all up for free from me 8-)