I too absolutely expect Apple, and other tech companies, to give this kind of answers. It seems like we have the same sort of experiences in the past. By the way, I wasn't aware tha I downloaded a beta version? I just got an upgrade notification in iTunes yesterday and I didn't read anything about a beta version.
However, my iPad now runs smoother than before and with iOs 6! Huh?
What did I do?
Well, As I said I decided to downgrade to iOS 5.1.1 and followed the instructions I found on the iDownloadblog. I just did a regular restore of my iPad, not realizing that the last backup was from yesterday, àfter I installed iOS6. But now it turns out that home sharing works perfectly with the music app. Furthermore, it even improved: it's now displaying the correct album covers with each album! Before they got mixed up, which is a rather common problem I found out a couple of months ago while searching the web for it. Oh, by the way, in the artist tab of the music app, the artist names still are not displayed correctly. But I don't mind since I only use the album tab.
To finish off, I must add that I also installed another virus scanner today (symantec to Panda cloud). I can't imagine this interfering with AirPlay / music sharing (a firewall could affect the ports AirPlay uses, but a virus scanner??), but I just do not want to be incomplete in letting you know what changes I've made.
In the meanwhile I keep my fingers crossed every time I start the music app on my iPad ;-)
Cheers
KG