I have really been enjoying Subsonic so far and have come across a few things that would make this project even better. One thing (and I know it sounds kinda petty) is the User Login is case sensitive. I usually make most of the logins lowercased (since most people are using it from their home computers) but from an Android phone, it automatically capitalizes the user login name.
Another idea would be to implement a failed login attempt log and maybe an account lockout for an account in case of an attack.
Not sure if you have much experience with MediaBrowser, but they have a wonderful virtual folder system that would solve the problem with multiple music and video folders spanning several different drives. It basically directs to a .vf file that has all the different folder locations listed within. http://www.mediabrowser.tv/forum/viewtopic.php?f=2&t=485
I think it just got mentioned, but it would be very useful to define what folders were accessable by different users.
Just my 2 cents on what may improve a pretty terrific project