While I admit that I really like iTunes, I am surprised that they make it such a pain in the rear to share music with another user on the same computer. I tried setting this up on my OS X box at home so my wife and I could share the music but have seperate logins. I can use the same folder, but can't use the same library file no matter how I change the permissions on the file, so whenever I download new music I have to login to my wife's account, delete the library, and rebuild it. It would be easier if they would just let you use the same library and have a seperate file for your ratings, etc.
Some Windows XP programs ask whether or not to install the program for just you or anyone who uses the computer and it wouldn't take much for Apple to do the same.