I've just had delivered a squeezebox. I've had it out the box to play with for a couple of days now and I've been very impressed.
http://www.slimdevices.com/
It works (which is more than can be said for my old Netgear MP101), it's 802.11g not b, it's also a wireless bridge for ethernet devices, you can control it via the excellent Slimserver web interface too (including album art etc), it syncs to itunes nicely but doesn't *need* to, you can have more than one of them and they will sync and let you do multiroom audio, and this includes the 'softsqueeze' client. Oh, and it's quite pretty.
Slimdevices have just been bought out by Logitech and it seems like they've committed to supporting them for a while (Roku seem to be focussing more on niche markets like display signs etc now).
The Sonos looks very nice too - but the geek in me prefers to slowly build my own equivalent with a mac mini as the 'music controller', some decent speakers, squeezeboxes as the client, and (at some point) a wifi pda to control it all (not that using either my macbook or the remote control is a bad way to control it
I had excellent service from Jon at
http://www.ripcaster.co.uk/. His distributor screwed him, so I ended up getting it from Dabs, but it was more expensive than ripcaster and he seemed like a very good guy to deal with (he phoned me at 7:30pm on a friday evening to process my refund!). He mentioned he also does home demos of the sonos. As ever when I recommend somewhere YMMV