I use a Person's Rating field with display of the first letter, such as B for Ben's Rating. This allows it to show very small. The issue is that you can't use stars, but only an integer. I created the new fields with integer values of 1;2;3;4;5. It's annoying to have to set them by typing so I can hope for the ability to make any field use stars.
To make it amazing but complex, don't store rating in the files. Instead, users can quickly rate songs and then I have a special playlist that shows songs where the Rating != Ben's Rating. Then, I can quickly update a list of songs by modifying the Ben's Rating field (or vice versa). The neat thing about this is that another user can rate a song for you through the Ben's Rating field but when you are updating songs, you don't have to follow the field. This is a validation step. Then, make sure to create playlists from Rating but be sure to update your ratings often or you'll get annoyed that ratings aren't showing up on your other accounts.
Then, with this method, you can easily create playlists that pull ratings from any users, and there isn't really a limit to the number of users you can have... A's Rating, B's Rating, C's Rating, etc!
Works GREAT.