Zimbra… Maybe?

So I’ve been playing around in the background with mail servers.
You may have noticed connectivity issues (especially today 12-23-2010)
as I’ve been playing with alternative imap servers.
We’re now using the imap server dovecot instead of wu-imapd.

I’m thinking about installing the Zimbra Open Source Edition.
It would enable a boat load of new features that I’ve been drooling over
specifically CardDAV, iCal and CalDAV for contacts and calendars.

Anybody have an opinion on this suite?
Or any alternatives that they may have used that they recommend?
I’m open to suggestions before I dick with Zimbra…

Thanks in advance.