The way Sonos works isn't immediately obvious so I hope it will help if I set it out as I understand it. For the review, just skip this bit. I put a copy of this review on the zone bridge page too, having reached the age where I repeat myself.
Sonos attaches itself to your wifi network and allows you to play music which you have ripped onto your computer eg using iTunes.
Sonos the company provides three sorts of device. They renamed them in November 2011, so I have included the new names too:
players - unamplified (eg ZP90, this item, which Sonos have now renamed "Connect"); amplified (ZP120/Connect:Amp); and amplified with speakers (S3/Play:3, S5/Play:5)
a bridge (BR100/Bridge)
a controller (eg Sonos Control or your phone, tablet or computer - the software is free)
You need to attach a player or a bridge to your wireless router, so if your router is in your living-room then you simply attach the zone player to your router and you're off. If - as at Casa Stevie - the router is in the hall then you need a zone bridge which you attach to the router so that you can have the zone player in the living-room. The zone bridge doesn't play music, it just provides a link to your router.
So to the review, which is of the BR100 and the ZP90. In the box you get the bridge, an ethernet cable and power cable. The zone bridge itself is small and not unattractive - like a smaller mac mini. You also get a sheet of paper which describes the 4 steps needed to set it up, the CD which contains the software, and a booklet about the system.
In the ZP90 box you get the player (again, nice looking, a bit bigger than the bridge) and likewise all the cables you could reasonably ask for: ethernet, phono-phono, phono-3.5mm jack. The cables themselves don't look very high quality and I'll replace them, but they're fine for the time being.
Set up is easy-peasy (I did it on my Mac and on a Dell laptop running Vista). The program automatically downloads the latest software and installs it. You then use the software to connect to the individual items (one at a time: not, as I tried to do, both bridge and player!) and then direct the system to the music library/ies you want it to use. I had 150GB in iTunes Media on my Mac mini (actually, on a Samsung Story hard disk attached to it) and it took about 20 minutes to index that. When I then added the iTunes library on Mrs Stevie's laptop, it took another 40 minutes.
Then it was time to listen.
Playing the ZP90 through the hifi (Cyrus 7 amplifier, Mordaunt Short speakers) really shows up the difference between lossless and lossy formats, so much so that you may decide to re-rip your CDs into a lossless format (as I have now done). There is a clear depth and spread in the lossless format (I'm using Apple lossless) that is completely missing in the compressed versions (MP3, AIFF, AAC etc). The good news is that hard disk space is cheap!
The sound quality isn't quite up to my (10-year-old) Musical Fidelity CD player, but it's surprisingly close, and certainly good enough for me to leave most of my rock and pop CDs in the attic having ripped them to Apple Lossless format. And the convenience of having all of my and the missus's CD collection available from our iPhones is terrific.
As you will have noticed, I didn't buy a controller (How much? They must be kidding) but downloaded the app onto the iPhones. It's great, and Mrs S is much less likely to lose her beloved iPhone than a controller. You can use an iPod Touch too, and Android phones etc.
And all this is without mentioning the internet radio which also is available on the Sonos and which works as simply and efficiently as the rest of the system.
Addendum for Mac users: in my original review, I mentioned as a slight problem the occasional failure to find tracks or delay in playing them on my Mac (not a problem on my wife's laptop). I thought it was linked to the external drive going to sleep, but I think I was wrong: a bit of research suggests that there is a problem if you're running your Mac on Airport (ie wirelessly). As long as you have a wired (Ethernet) connection for the Mac itself - the Sonos kit stays wireless - then it works.
I don't think it's a problem which affects PCs - certainly we've had no problem with the laptop which is wireless.
Sorry for the long review.