Best wireless multiroom system for music lovers
The Sonos System is one of the best multiroom systems available. It needs a server with your music (can be any PC), no built in storage. Easy to set up (

Absolutely the best
This is by far the best thing since sliced bread. The installation was very easy and fast and the software controller all work flawlessly. The ability to control music from my iphone is amazing. I can now control what I listen to and where with such ease- I am beginning to like music even more!
These guys really did it- Keep up the great work Sonos!

Better than Squeezebox Duet and less expensive than expected
I had owned the Squeezebox Duet for about a year, using it to control music in one or two rooms. (I have a wired connection between the two rooms, which I control with a manual switch.) Primarily I listen to music from the Internet-based provider Rhapsody. Although I liked the look and feel of the Squeezebox system and controller, it would not work reliably in my two-story home, where I have a wireless router upstairs and used a Squeezebox receiver downstairs. Every day or two, the remote controller would lose contact with the receiver (or maybe the receiver would lose contact with the router), and I was forced to try to reset the system. Sometimes this resetting process was relatively simple (just turn off the controller and then turn it on again, which takes a minute or so), but more often it was quite laborious, requiring me to re-enter the router's 22-digit security code by using the controller's wheel to scroll through all the possible combinations of lower and upper-case letters, numbers and punctuation marks. Even then, it would sometimes fail to connect, and I would give up in frustration. The Logitech support people were great, and they even gave me a brand new system to try, but it still kept crashing.
Finally I decided to try the Sonos system instead, even though it was considerably more expensive than the Squeezebox. I was able to save quite a bit of money by buying just 3 items: the Sonos Zonebridge 100 (which connects via ethernet cable to my router upstairs), the Sonos ZonePlayer Z90 (which connects directly to my amplifier downstairs; I'm using an optical cable which may improve sound quality), and an Ipod Touch 8 gB (2nd generation) as a wireless controller. I saved more than 0 by buying the iPod Touch rather than the Sonos wireless controller (actually 0, since I didn't have to buy the charging cradle for the Sonos controller). I'm much happier with this new system.
Setup was fairly easy, compared to the Squeezebox. Getting the iPod Touch to work as a wireless controller was the hardest part. After completing the setup for the Sonos components, which was simple, I connected the iPod to my computer which opened my iTunes program (I already own two other iPods). I had to tell iTunes not to synch my music to this iPod, since I plan to use this one only as a controller for Sonos. Then, in iTunes, I went to the iTunes Store and searched for "sonos iphone app." This search produced two results, but one was a podcast. I downloaded the other one, called simply "Sonos Controller" and then synched it to the iPod Touch using iTunes. After ejecting the iPod from iTunes, I began using the Sonos Controller on the iPod. At some point, I was prompted to enter that all-too-familiar 22-digit security code for my router, but this time it was much easier, since I was entering it on a virtual keyboard on the iPod screen rather than trying to use the Squeezebox wheel system. It was helpful to watch the Sonos video demonstration of the Sonos controller on an iPhone (found on the Amazon screen describing the Sonos BU150 Multiroom Music System) to see how to control volume etc.
There are several advantages to this Sonos/iPod system, compared to the Squeezebox, and two disadvantages. Advantages: 1) the Sonos/iPod system doesn't crash (But I did have one difficult problem after a few weeks of use: Rhapsody's list of my favorite channels stopped working and we tried removing the Rhapsody service from Sonos and then putting it back. When I tried to put it back, the Rhapsody server refused to accept my user name and password. Getting this fixed took 3 long phone calls to Sonos and Rhapsody and more than 24 hours of downtime.); 2) the iPod holds its charge for about 5 days with normal use, compared to a day or so for the Squeezebox remote; 3) it's much easier to search for music using the iPod's virtual keyboard, as opposed to the Squeezebox's awkward wheel, and this difference is huge, since searching for music with Squeezebox was so difficult that I almost never did it; 4) I can slip the iPod into my pants pocket and carry it around the house without fear of dropping it or accidentally pressing keys that might stop the music; by contrast, the Squeezebox controller is too big to fit comfortably into my pocket and, if I did put it there, I would be very likely to press buttons and produce some unwanted activity. Disadvantages: 1) the Sonos/iPod system cost me about 0 more than I would have paid if I'd purchased a new Squeezebox Duet; 2) the iPod goes into a partial shut-down mode after about 50 seconds, so if I want to adjust volume or change tracks, it takes longer (about 6 seconds total) to perform these operations using the Sonos/iPod system, as I must first turn on the iPod (by pushing a button and sliding my finger across the screen) and then wait for it to reconnect with the Sonos transmitter.

Nice product with serious (undisclosed) limitations
I found out the hard way that the Sonos has a very serious limitation if you have a large iTunes library (or even several of them) that you intent to use with the Sonos. If you have more that 40,000 tunes in all of your playlists, Sonos will not import them. That sounds like a lot until you realize that according to Sonos one song appearing in four playlists counts as 4 (virtual) tunes!

I have around 20,000 tunes total in my iTunes Library but racked up ~54,000 virtual tunes across my playlists. The 'solution' to this issue was to delete playlists (aka forgo organization and ease of use) until the total number of virtual tunes was under 40K.

It is important to note that this limitation is across *all* music libraries that you want to access via Sonos. So, if in you family, your daughter has an iTunes collection, as does your wife as well as your own, you could quickly exceed the capabilities of the Sonos. When I asked a Sonos representative if this was a temporary limitation or one that was going to be fixed in the future the rather indignant answer was "No, we have no plans on fixing this."

Other, much less expensive options from Roku and SlimMedia (now Logitech) don't have this limitation, so if you have a large iTunes library you probably want to weigh your options.

Buyer beware.

And then there was music....everywhere!
Wow! Months back, I was sitting on a friend's patio when her husband handed her a little white box not quite as big as a cd cover. She appeared to just press a couple of buttons and then whoosh! music outside. "wait, I think I want to hear something else" and then ding - a new song, "okay, that's good for us, now how about the people in the kitchen?" she said, "..let me put something different on for them. And maybe something else in the kid's room" "What the heck is that?" I asked. She told me it was a Sonos player and that it wasn't cheap but was fantastic. Well, after thjinking about it for quite a while, we did get one which enables us to have different music in two different zones. For four zones, you would need a second sonos player. It is easy to use and with some bose speakers we finally have fantastic music with scores of ways to have songlists and searches. It's really been ideal.