Just so I am being perfectly clear - Sonos has no integration with MC at all...
In fact, it has no integration with any Music Management software and does not require any server side software to be running or a PC to be turned on. It indexes its own library based entirely on id3 tags - which makes MC an excellent tool to manage the library.
You cannot customize views and only have the stock ones available to you which are artist, album artist, genre, album, composer and track. For me, I have rethought my library to meet with this restriction and though I know I am losing functionality and customization, it is a trade-off that is more than worthwhile to get the benefits of the Sonos.
I use a couple of genres to indicate "current" albums - [Current - Country], [Current - Jazz/Vocal] and [Current - Pop/Rock] to make the albums I am enjoying now more readily available. I also have a genre called [Greatest Hits] as I enjoy collecting Greates Hits albums for some reason. In the end, I find the library searching by Genre very usable. By only populating the Album Artist for my complete albums or albums I want indexed in that view, it is also possible to keep a more concise listing of tracks available in Sonos. In the end, I have almost completely reworked my organization method but I am quite happy with the results. I have about 25,000 tracks in my library. It reindexes the library in less than a minute and can be set to do it automatically over night.
I should mention that it uses the J Rivers tag Band for Album Artist, which is unfortunate though just a matter of getting used to. I found this out by reading that Itunes does the same thing so I hardly blame Sonos for this.
As for playlists, you can export MC playlists by selecting Export all Playlists from the menu. This exports all the playlists, including smartlists into .m3u playlists. These playlists are imported by Sonos and placed in a section of the library called "Imported Playlists" which is easily accessible from the front screen on the controller. Try exporting your playlists and see what the resulting .m3u playlists look like. This is how they will appear in Sonos.
I don't find this ideal but it works fine for my needs - though I have never been a heavy user of playlists. Recently I have found myself spending more time with the smarlist functionality in MC to build some more customized lists for my Sonos.
No matter what, songs played on the Sonos do not update play counts in MC and so playlists which are dependent on those will not work.
Last.fm is not something I have used at all but there is an app for Sonos which will submit play data to last.fm
http://www.purple.org/sonos/ Maybe there is a way to use that data in MC - I don't use last.fm at all in MC or Sonos... Just offering an idea there...
I *suspect* that you may see the day when Sonos opens up to other upnp servers and that will be the opportunity to more closely integrate Sonos with MC, but there is no discussion about that at all by the developers at Sonos but they do use upnp to integrate with rhapsody. As a side, Sonos also has tight integration with Rhapsody's service which is really quite neat. It comes with a 30 day trial but I found myself really liking the way they worked together and am trying it out for a few more months. It's neat to have access to 3 million songs from a little handheld controller...
I spent *a lot* of time playing around with NetRemote and trying to get it to do what I dreamed it would - customized just for me and got quite close. When I held a Sonos controller in my hand, I fell in love and ordered a system the same day. I couldn't be happier and even my wife wouldn't give it up and shes never been able to use any of my other attempts to make this work. We listen to *much much* more music than we have in years and the Sonos is the only reason why.
I really couldn't say enough good things about Sonos. They have a 30-day money back guarantee if you want to try it out - but I'd bet that once you got them into your house you wouldn't give them up...