D,
I've been using Sonos with MC12 for over a year now. Perhaps like you, one of the main reasons I love MC is because of the ease in creating playlists and smartlists, and I've created dozens of them for just about any situation or company that comes over, and I play them all the time on the sonos devices. I have been able to link up the MC playlists in the Sonos software and controller without any problems. It's not perfect because there is no pure UPnP compatibility, so it's not seamless and instantaneous, but the steps to synch are pretty easy and fast. This has worked for me for all my playlists and my smartlists.
Some of this may be too obvious, but sometimes the obvious is the problem:
I click on "export all playlists" and send them to a specific folder. You can change the destination in the options dialog boxes. Make sure that the MC options are set to export them in a .m3u format, which Sonos recognizes.
Once you specify the folder to receive the playlists, open the library options box in the Sonos software and click on "create a share." browse to the same folder that you selected in MC12 to receive the exported playlists.
(If you're running the sonos software on a different computer in your network than the MC computer, make sure the folder that contains the playlists is shared on the network. I don't see why you would have to do this if the programs are running on the same computer.)
After you have exported the playlists, update your library in the Sonos software.
Note that your imported playlists will not be found in the "Playlists" section of the sonos software. when you are using the sonos controller, you have to click on the Music Library, then scroll down to "imported playlists." it's an extra step, but not such a big deal.
If you're still having problems, write again. I'm putting this together from memory at work, and I could walk through it at home. If you get it to work, do us both a favor and send sonos an email asking them to change the sonos software so that the imported playlists don't show the .m3u file extension in the displayed name--seems pointless to me and the sonos guy told me when I asked that they could change the software but haven't because not enough people need it!
Plus, if Matt or any of the other MC12 developers are reading, how about a function where one can select a number of playlists to export? right now, it seems to me that you can either export one or all, and nothing in between. Maybe I'm missing something.
The point is, it does work for me. I know there are many MC12 users who are sophisticated network folks (search "doof") who synch zones using MC, but the sonos system is so easy and sounds so good. I have half a dozen all around the house and I use them literally every day. my six-year old can even play the music he likes.
John