I finally upgraded the other mac in the house to run iTunes 4 today. It took a while to get playlist sharing up and running, because both macs are running firewalls. Rendezvous can find that there are iTunes available for streaming, but that's separate from browsing and sharing. Surprisingly, the iTunes help doesn't mention this at all (or if it does, I got tired of trying to find it).
Opening up port 3689 alone seems to be sufficient for music sharing.
Music sharing is the one iTunes feature I've wanted for months. I keep all of my MP3s on the iMac, and about a day's worth on the iBook. This will certainly make it easier to manage music on the iBook now. One nit I have is that when playing a stream, none of the playcount/lastplayed fields get updated. While this is correct in the majority of cases, I'd like to see an option to keep this data synchronized somehow. Whether I've listened to one of my tracks directly or from a stream, I've still listened to it, so it should move to the back of the queue.
