So far FireFly is working great. iTunes is nowhere near as good as MC, but at least I have access to my full library on my Mac. All I needed to install on the server was FireFly (
http://www.fireflymediaserver.org/) and Apple's Bonjour for Windows (
http://www.apple.com/support/downloads/bonjourforwindows.html). On Windows, FireFly is still not released as a stable build, but it's been working for me so far.
On my server, I have:
MC 12
Firefly 1586
Apple Bonjour for Windows
Now I can:
Play two zones of audio via MC and my separate audio processor using MC and Girder.
Access my library from MC on my one remaining PC laptop.
Access my library from iTunes on Mac or PC.
Access my library from two UPnP servers (Firefly and MC). I have Rokus.
Note, FireFly does not give you any real control over transcoding. Basically, it transcodes everything to WAV. That's how it works from my WMA Lossless files to iTunes. At least it only transcodes if the client doesn't support the original format.
It would be awesome if the iTunes functionality could be rolled into MC as a plugin. Given that the code is open source, it should be doable. If I wasn't already starting a company, I would do it myself, but my time is very limited.