We're having almost the same issue Wryce. I want to control what's being viewed on each client my self. I'm living in an apartment with several users that want to share my library. But I do not want to share all of it with them, and I do not want them to touch my tags, or that they update my play counters etc.
I think that the Access Control might work if it can be applied to the clients. But it's kind of strange that I have to set this up on their computers. It will not prevent them from updating tags on the media that they do see either I think? So, it's a no go for me. Let's hope that this access control list is improved with a user system later on. Much similar to Active Directory in Windows. You'd have to identify your self to view the media, and read/write access would be totally configurable on the server. That would be something.
I think a system where you set read/write/deny access to different users on each Media Sub Type would be enough in most cases. And that each user get their own set of Play counters, last played, number skipped etc.