Is the iOS 5 beta no longer usable? I've been using iOS5 beta 7 for a while.  About 4 hours ago (possibly the end of the 20th, PST, the expiration date for iOS 5 beta 7) the phone locked itself and claims it requires activation.  Whenever I try, it claims the activation server is temporarily unavailable.

Should I sit tight and wait, or is there something else I can do, such as wipe iOS5 and reinstall from a release image?
You'll have to upgrade to the release version, not much else you can do about it.