"clean" migration from 5.0.18 to 6.0.x using imapsync

[mfehr]

I plan to upgrade my 5.0.18 Zimbra server based on Ubuntu 8.04.2 32 Bit to 6.0.7 (once available) on Ubuntu 10.4, potentially 64 Bit, in VMware server. The easy migration procedure recommends to rsync the /opt/zimbra directory, install the same zimbra software on the new server and upgrade afterwards.

I use Zimbra since version 4.x. Hence the /opt/zimbra directory collected more and more old data like a ton of zmstat data, various jdk directories, multiple clamav version directories, etc.

My users only use Mail and calendar. On the other side, before I want to cut over, I would like to test the 6.0.x environment. On the Zimbra wiki, I found a description how to syncronize with a 2nd server using imapsync. imapsync also allows me a simple downgrade if necessary.

What are the implications when I use imapsync instead of rsync-ing /opt/zimbra? imapsync ensures proper e-mail synchronization with the new server. User accounts and passwords are under control, user preferences must not be taken over to the new server. However, what about
calendar data?
SPAM training data?
Other data I should be taking care of?