Super Priority Inbox
avc.com
avc.com
Every layer of priority added increases the chance of your actual inbox effectively becoming an ignored "spam" folder. Any mail that isn't correctly classified as "super priority" will be missed. How much time do you really spend deciding if you need to respond to this person immediately or read later?
I prefer to use classification for context. I want to see all mail associated with client X even if it's from/to multiple addresses. Or all mail associated with system Y. If an email is Ultra-Hyper-Priority that will change the second I respond to it. But a year from now I might like to know how I responded to a similar question/context in the past.