I've always used Sonos (for more than 10 years now) and I agree they have a very good product, albeit pretty expensive. I even kept Sonos in mind when I built my house and had ethernet and speaker cable connections in every room (and room to hide away the connect:amp, mostly in closets), just to be sure it's mesh network would work optimally. Of course, now we have smart phones and wifi and so all my Connect:Amps ended up on top of each other on a shelf in my tech room. I agree with Matt this looks silly.
I would much rather have it that Sonos would release a rack-mountable solution that would harbor 4 or 8 zones. Kind of like Denon does with their Heos series.

Another department where Sonos fails miserably (and it's by choice), is its virtually non-existent way to integrate it with a home automation system. Sure, there are ways, but they have always been achieved by reverse engineering and never get any support from Sonos.
Sonos also doesn't support Airplay. And never will because it's hardware design is too old, trapping them somewhat because upgrading their hardware would make the new hardware incompatible with their older systems. Of course that would not be a good thing for them. For this same reason the maximum number of tracks on a Sonos system is 32768. This cannot be upgraded for the same compatibility reason I mentioned earlier.

It's for all these reasons combined I've started to look out for alternatives. Like eg. the aforementioned Denon Heos system, or CasaTunes. Because there are other systems. It's just that Sonos has a helluva good advertising department and these days they've somewhat completely swamped the market. But they do have nice products which function extremely well, be it with some flaws.