I have the open source edition, and just did an upgrade from 3.0.1 to 3.1 (on RH FC4). It went flawlessly- and I just wanted to say thanks for an amazing product, with a super easy upgrade path.
I have only about 20 accounts, but one is large (mine) and it's about 30gig of email alone.
Thanks again for an amazing package- you've changed how I do email, and I'm trying to get whomever will listen to me to check out Zimbra.
Now, if the IDLE command is working on the new IMAP server, my Treo's email client (Chattermail) is going to fly like it used to on Cyrus IMAP.