I got one of these last month. The sound is definitely not as "crisp" as the Klipsch 2.1s I have but it still sounds better than a lot of other "all-in-one" units I've heard. The Sonos solution as a whole is really top-notch.
I recently got two S5's and a ZoneBridge. Love the sound so much, I went back a week later and bough 2 more S5's to fill out the house! The sound is much better than what I expected, and they are incredibly easy to setup & use. Of course, they are not the best sound compared to high end speaker systems, but they do a great job across lots of genres & internet streams.