Upgrade from ZCS NE 5.0.18 to ZCS NE 6.0.0 GA on RHEL 5.3 64bit with ZCB 5.0.18
I just shut down Blackberry Controller service, done a backup of my 5.0.18 NE on RHEL 5.3 x86_64 and run the 6.0.0 GA installer - All working.
Outlook users with Outlook Connector 5.0.18 aren't reporting any issues (OK I only have 20 such users so my install-base is hardly indicative).
Blackberry Connector 5.0.18 seems to be working also as my BES users (8 total) aren't reporting any dramas either.
I love Zimbra - well... despite their RedHat marriage and their refusal to support CentOS :)