Some problems I encountered when upgraded from GA 3.0 to 3.0.1.
The server original version: GA 3.0
hostname: moon.example.be
email domain: example.be
-> Stopped zimbra with zmcontrol stop
-> Make a copy of /opt/zimbra to /opt/zimbra_GA_3.0
-> run install.sh
-> select upgrade
The first problem occured because I don't have an MX record for "example.be", so Zimbra suggested the "moon.example.be" as new mail domain and didn't know that I was upgrading from the "example.be" domain. I did choose to not enter a new domain and continue.
Now the real problem occured when the script tried to get some information from the LDAP server, The script didn't know on witch port http an https zimbra should run. I did told the script port 80 and 443, returned to the main menu, but the script didn't allow me to apply the changes. Then I "Ctrl + c" the script.
....
Drink strong coffee

...
-> Started zimbra with 'zmcontrol start'
-> run install.sh
-> select upgrade
Zimbra complained again about not finding a MX record for 'moon.example.be', but just ignored it again and the script continued.
Now the script found the information in LDAP, so it found the http/https port that Zimbra was running on originaly.
So far so good ...
The only issue I encountered then. The script still wanted to create a new domain 'moon.example.be', so I told not to create the new domain.
Applied the changes and zimbra upgraded and started just fine
So after this story ,I would suggest:
1) Let the script check if LDAP is running, if not let the script try to start it up or give a warning.
2) The script didn't know I use the email domain 'example.be'
3) It's not because the hostname is 'moon.example.be' that I want to create a new email domain 'moon.example.be'.
4) Because the translation files are not included in the zimbra package , and the script didn't make a backup of those files they where lost.
So before upgrading, Make a Backup! And check the settings that the install script suggests at the end.