For several years now I've been trying to find a good way to serve music to my bedroom upstairs. There are speakers in the ceiling of the bedroom and bathroom up there, and now that all my music is digital I've been working on a good way to stream it to that location. My house isn't wired with network cable, and the layout of the place makes doing so rather challenging (no attic or crawl space, etc).
Since I'm running Media Center now, one idea would be to get an extender to do it, but that's a heavy weight solution. Not only do you have to buy a TV and an extender, but you're dealing with turning all that stuff on just to listen to music.
One thing I tired was the Creative Labs SoundBlaster Wireless Music. This basically does what I want, and even though the remote looks big and clunky, it's nice because it has a little digital screen that you can browse through the music with, rather than having to go over the the receiver.
Its wireless, so all you need to do is plug the receiver into your stereo and you're good to go.
When this worked, it was pretty cool. The remote was RF so you could use it in a different room, which was also nice.
Unfortunately the whole system was pretty flaky. The Wi-Fi support was sketchy at best and it didn't deal with my wireless network very well. It would randomly lose it's connection or stop playing. The remote would lock up. It wasn't quite ready for prime time.
The other issue was the software. You had to run a server application on a machine to serve the thing. Plus, that server app could only access the library out of another (proprietary) media organizer application. And it wasn't a service, so you're machine had to be logged in as well. If it ever rebooted due to a power outage or, more commonly, an update, your music no-workie.
When I changed out my office machine and put Vista on it, I gave up on this system. But I didn't give up on my dream!
A few weeks ago, I saw a good deal on the ROKU SoundBridge M1001. I'd seen these things around but had never given them much thought. I thought I'd have to go futz with this thing directly to select music, which seemed like a pain. I looked closer and saw that it had a remote. But what I really liked about it is how flexible it was - it plays almost every format on the face of the planet and works with Windows Media Connect (now part of Windows Media Player) - so it can directly access my music library WITHOUT installing any software. It wasn't too expensive so I ordered one up, and it showed up at my house after a few days.
The unit is actually much better looking than it is in the pictures. It's mostly made of metal and has a solid feel to it. I plugged it in an initially had some trouble getting it set up. Some of the early menus are confusing and if you skip a step, you're kind of in no-man's land. Once I figured that out and reset the unit, I was basically done. It set itself right up, and automatically discovered my music library. All I had to do was go down to the computer and tell Windows Media Player to allow it access. That was it. Seriously. Since then, it's just worked.
It'll work with wireless or Ethernet. So along with the built in WiFi support, the back has an Ethernet port, an optical port, a coax port, and a regular headphone-style port. 
It supports uPnP so it shows up as a network device in Windows. With a simple right click, you can get onto the devices web page that lets you configure all kinds of things about it. The manual also has a section on how to hack it - it also has a Telnet server built in. I haven't dug into that yet, but it's definitely cool.
The interface takes a minute to get used to - all the buttons on the remote only have glyphs versus text on them, but the UI says things like "Press EXIT to continue". Uh...riiiiight. After I figured that it it was smooth sailing. Once you've figured out which-buttons-are-which, the UI does allow you to flip through large libraries pretty easily.
Another big upside of this is that it allows me to play DRM'd music (grrrrrr....) around the house. I'm not sure if the server is doing the transcoding, but I am able to play music that I download via my Napster subscription.
So basically it does everything I wanted a device to do, and it does it well. I've been using it for about a week without a single connectivity hiccup, etc.
But the real bonus here has been the Internet Radio support. Wow - unbelievably cool. If you go out to RadioRoku.com you'll be able to browse through some of the 3,500 (yes, that's right) radio stations available. Basically since I've gotten the ROKU I've barely listened to my own music. The radio stations (SomaFM, RadioPardise, Virgin RadioUK, even our local NPR station) sound fantastic and you even get title information on the display when you play them. You can then use that web page (unfortunately it requires a very slow and painful Java install) and it will automatically update the favorites and preferences in your ROKU device. Again, wow.
Note it also works with iTunes; I'm not an iTunes user so I'm not sure what the experience is like there, but given the rest of the experience I'd assume it's good.
I'm strongly considering getting a second one of these for my mainfloor system that runs the speakers in the kitchen, living room, and deck. For the price (I paid less than $150, shipped), it's really a cool gadget.
With the exception of first 30 minutes of setup confusion (some of which can be blamed on my network), this device has one of the best end-to-end experiences I've seen for a while. Great job to the folks at ROKU, I wish I'd have discovered this years ago...