And yes, I use AllMusic as a guide for my tagging. The thing that prompted this is that I felt I had too many genres. I wanted to consolidate genres like Pop, Alternative and Rock into the more universal Pop/Rock and still use smartlists to create and Alternative-only playlist, or a Pop-only playlist, etc.
Part of my testing also utilizes the Moods and Themes field from AllMusic. The thought being I can take all the tagged info (genre, style, mood, theme, intensity, BPM, rating) and create playlists for things like snowboarding, driving, dinner party, etc. Like I said before, I'm a bit on the OCD side with it comes to organizing my digital life.
For example, I also have a Live field since I have a lot of live albums. I classify each live album with either "Official" or "Bootleg." This allows me to prevent poor-quality bootleg recordings from entering some of my playlists.
Always looking for how others classify music. If it works for one person, it may work for others (maybe I should start a new topic for this).