Vox Populi: How are you using Mail Tags?

I open the floor to all of you on a question of particular personal interest to me: How are you using Mail Tags?

While my uses of it to date have been helpful, I keep getting the feeling I’m not getting all that I can out of it – especially since the ability to associate Projects, Priorities, etc. to a message could make for some really enticing Smart Folders.

I wonder if my question is ultimately more taxonomic in nature – ultimately more about Spotlight in general or Tags in very very general: When tagging items on your Mac, what kind of ‘-onomy’ are you using? How strictly do you enforce your vocabulary? What are the best practices for someone who’s new to this?

Confidential to Mr. Thomas Vander Wal: if you turn up here and school me a bit on this, I’ll totally buy you a Coke. If you write a guest post on it, I’ll buy you a beefsteak and two cocktails. Seriously. Steak.