I got a bunch of the following errors:

Lost transaction log file /Users/frohro/Maildir/dovecot.index.log.2 seq 1

when I was trying to apply some rules to move messages from one mailbox to another.   Things hadn't been working well and I had recently upgraded to alpha 2, so I moved all dovecot* files in my Maildir/.

Things then seem to work better.

Rob