I did not find a thread specific to this topic.
After downloading the latest Network version, backing up the Zimbra datastores then the entire structure I started the upgrade.
It took a little bit of time, stopped, started, stopped restarted some services while the database and ldap modes where executed, and ran to completion.
I had a number of concerns based on prior installation nightmares, fits getting certs installed and problems with FireFox POP function under RC2.. so it was a fitful process.
My hat is off to you guys at Zimbra. The install executed without a hitch!
* SSL Certs - all our commercial certs were retained and TLS testing with our client looks promising.
* Firefox POP3 (and I'm assuming IMAP) access FIXED!
Congratulations guys. Work well done, and you got it out before the end of the rear.
One really minor nit-pick. Someone misspelled 'certificate' in the Admin interface.

If that's all I have to worry about, then we just need the contact info of your sales department so we can buy the full license!
The bonus for my team is that this release let us meet OUR deadline and have new mail services by the first of the year.
Kudos. Now take the rest of the year off, you deserve it!