Actually the Squeezebox server software is very agnostic as far as OS use goes. It is open source and written in Perl with versions readily available for Windows, Mac and Linux. I know quite a few Mac guys using the Squeezebox, although I have no idea why they selected it over the Airport Express as the AEX looks like a nice solution if you are Apple centric. I do like the fact that the Squeezebox is open source and I’m not tied to i-Tunes with it.
I have two of the SBs and am using Linux as the server with the CDs ripped to FLAC.