I'm not really satisfied with UofW imapd and it's own pieces of peculiar, but everything else I looked at wanted me to change mailbox format (maildir might be ok, but I'm _used_ to mbox, comfortable with it, and don't feel like changing).
In any event, it looks like dovecot might be what I want. It supports mbox and maildir, IMAP4rev1 and pop3 (both with ssl using gnutls or openssl) and ipv6. It seems to be coded with some intelligence and uses index files that are external to the mbox for speed (yay!). Mac OS X (10.2) is even listed as a system that it is "known to work" on.
I'll have to set aside some time at some point to play with it to make sure it will work, but I'll probably move geeklair.net over to it eventually.
Oh man. And this does LDAP auth. I think I owe you for this one, since I was wrestling with Cyrus and Courier and not happy with either. :D
Are you going to be setting it up with mbox or maildir?
Let me know how it goes in any event.