currently I am running Zimbra 4.0.4 on a server with Ubuntu 6.0.6.
I want to migrate to a new blade server SLES 10 and Zimbra 5.0 beta.
On the first server I have only 6 accounts (it was a test server for months), so I think that the fastest upgrade would be:

1. create accounts on new blade server;
2. copy messages with imapsync: freshmeat.net: Project details for imapsync

it's ok for you?