Alas, I don't think so. It also doesn't really work if you let your number of Unread messages grow without bound, since it's only looking at how many messages you've read but left sitting in your inbox.
I personally don't like the priority inbox concept. I really want to have full control over what I allow to go out of sight out of mind. If I got a truly overwhelming amount of email then I guess I'd be happy to trust that to Google.
In a sense I do have an overwhelming amount of email but not so much that I can't at least look at everything that comes in and decide for myself what can be ignored.
Gmail is a bit inconsistent about that by default: it shows you the number of individual unread messages, and then the total number of threads, so you can't use subtraction to get an accurate read count. GmailZero gives the number of fully read threads (unless you have a really huge inbox, in which case it counts the bare read msgs until you get down) -- so if a thread has an unread msg it goes back to an unread thread and doesn't count against you.
