An unfortunate side-effect of having a lot of music in iTunes is, of course, managing all those songs.

I've gone through and tweaked my genres a lot. Since a lot of "classical" isn't actually classical music, I've created "contemporary orchestral" and "contemporary opera" and "baroque" and "renaissance" to split them out.

I've similarly broken out progressive rock from "rock" (because it's a significant sub-category in my library).