We are looking at Zimbra as an alternative to Exchange 2003 in order to reduce our licensing costs.

Has anyone done this? We currently have Exchange 2003 Enterprise with about 150GB of emails stuffed in it. The organisation has about 50 users and are very Exchange centric in that people here use a lot of the features (public folders, folder sharing, opening other peoples mailboxes, Out of office etc etc). They use Outlook exclusively and are required to do so by the line-of-business app they use.

I'm looking for peoples stories about doing something similar. Any gotchas, any issues, any migrations gone wrong, any issues with reproducing the above in Zimbra etc ?