I found the Sirocco an interesting little device. It was easy to set up and fun to play all of my PC-based audio out through my stereo without hassling with DRM. And I was also pleased to find its undocumented ability to be an access point, but there's no guarantee that that functionality will stick around with firmware updates. I would have liked to see Apple support on the device, and I heard a couple of audio dropouts while using it, but that's hard to completely avoid any time you're wirelessly streaming audio.
As far as a comparison to other devices, the most direct comparison would be to the Apple Airport Express. Both devices have similar wireless client capabilities, lack an interface on the remote side, and rely on the computer for selecting and playing back audio. The Airport Express is available for both Windows and Mac OS systems, whereas the Sirocco is Windows only.
Like the Sirocco, the Airport Express a no-brainer to use. It is directly incorporated into iTunes and requires only a single menu selection to turn it on. But the Airport Express' iTunes integration also limits it to only that application, where the Sirocco can play any audio that can come out of your PC's speakers.
In addition to its audio capabilities, the Airport Express officially supports configuration as an access point and has the ability to be a print server. But if your main focus is audio, the Sirocco has digital audio output, compared to the analog-only Airport Express.
I'm an iTunes-only user with both Windows and Macintosh systems on my LAN. I appreciate the seamless integration and flexibility of the Airport Express, so for me it's a better fit, and I'd have no problem recommending it. But if you're a Windows user looking for a way to play a mixture of audio sources to your stereo, the Sirocco is the clear winner. It can play audio that the Airport Express can't and its digital capabilities give it a sound-quality advantage.