I've used a Sonos for a while and found the Mk1 remote very 'laggy' in use. I'd heard great things about it but wasn't actually very disappointed when i finally got to use it. The touch wheel also seemed very flaky.
You should look at Logitech Squeezeboxes. You can achieve the same as Sonos for less money and get a far more flexible system as well (not least that you can continue to use whatever HiFi kit you've already got rather than using Sonos integrated amplifiers). I've had Squeezeboxes at home for years and the software and hardware has got steadily better. The new Squeezbox 'Touch' looks very cool – full colour touchscreen player that will display album art.
Personally I'd avoid the Squeezebox 'controller' and buy an iPod touch and download the iPeng contoller app (cheaper as well). You can then combine it with either Squeezebox receivers or Touches in each room depending on whether you want a display. You can play music synced across different rooms or different music in each room.
We've also have an iMac (that acts as the server for the Squeezeboxes) that i use with my iPhone as an iTunes remote and it works really well but the lack of 'on the fly' playlists on the mac is really limiting – Squeezebox has the option 'add to end of playlist', 'add to playlist to play next' as well as 'clear current playlist and play this song'.