When you open an IMAP server with say 100000 folders that you can view, it tries to cache status about *all of them*. This makes it sort of suck, in the "my machine has become unusable" sense.
Until now, my workaround was "add additional users each of which has a different IMAP prefix" (archive is one example. org.acs is another).
My new solution is more gross. Go into /System/Library/Frameworks/Message.frame
Ok, now, as long as you have useful subscriptions, Mail.app now performs much, much better.
