OK, thanks! I'll probably do the safe thing: Do a full image backup of the OS, a library backup, and finally renew my full music backup (exact copy on an extra set of disks that reside in my carputer). Then I'll uninstall MC11.1, install MC12 and try it with a few operations for a week or so. For my part it's really easy: If multizone playback of MP3 files, tagging and NetRemote control works, I have all I need. I don't use any of the more advanced features, the portable players, anything at all DRM and so on. The playback I have tried for a long time with my office computer and notebook. The NetRemote control I have working on another computer that will replace my main Internet and file server (not media server) in a few days.
The only thing I haven't tried is the tagging and management. Doesn't seem like there are any hughe bugs with that as of now, I only save artist, track number, track name and album name to the files. The rest is purely in the library. I tried to work without anything saved to the files, but it turned out that the track names could change to incorporate the track number as well, so I had to save some data to the files. Oh well, can't win 'em all.
OK, off to do my backup chores...