Hi
I have considered the idea, but we just change from mbox to maildir about 4 months ago, and we have many problens with some accouts. We were using dsync to migrate.
Out of curiousity - how did the backup times change between mbox vs maildir? I would suggest that this gives you a baseline for how much performance you could recover by switching back to something which is kind of an mbox/maildir hybrid?
But once we choose mdbox we are sticky to dovecot, or gona have to migrate all users again if we choose to use another imap server.
True, but seriously, what are your options these days? Dovecot, Cyrus and ...? If you switch to cyrus then I think you need to plan your migration carefully due to it's own custom indexes (so maildir buys you little). If you move to MS Exchange then you still can't use raw maildir. Actually apart from Courier is there another big name IMAP server using raw maildir?
With that in mind perhaps you just bite the bullet and assume that future migration will need dsync again? It's likely to only get easier as dsync matures?
Good luck
Ed W