MacInTouch Home Page: "[Mathew] I upgraded to iTunes 4.5, and discovered that it would no longer connect to my jukebox machine, which has my entire music collection on it. The machine is a Linux box running the open source daapd software, which implements the daap protocol iTunes uses. The server also broadcasts via Rendezvous, so it works exactly like a Mac sharing via iTunes.
Fortunately I had purchased iLife, so I had the iTunes 4.2 installer on CD. I tried to downgrade, and discovered that the iLife installer wouldn't let me, even if I trashed iTunes from the hard drive. The solution to that problem was to go to /Library/Receipts and remove the iTunes.pkg and iTunes4.pkg directories using sudo rm -rf iTunes*.pkg in terminal; having done that, I was able to install iTunes.
The next snag was that iTunes 4.5 had silently upgraded my music library and iTunes 4.2 wouldn't read it any more. Luckily, since I keep all my music on a central server, I didn't need the local library, and I just trashed it. There was a file called 'iTunes 4 Music Library (Old)', perhaps that was a copy of the old version?
So, it seems that iTunes 4.5 once again makes an unannounced change to MP3 sharing. For me at least, iTunes 4.5 is a no-go until someone fixes the incompatibility with daapd.
While I'm writing, my biggest gripe with iTunes is that I can't make playlists of shared music tracks.