I installed Zimbra iSync connector 4.5.753 and set everything up to sync my address book entries and my iCal with Zimbra. I noticed that my address book entries transfered through to Zimbra ok with some caveats:
1.) A bunch of the entries in Apple Address Book do not transfer (IE: AIM/Jabber info, website address, birthday, etc...etc...). Sure, I could custom create these entries in Zimbra, but if the point of the connector is to truly sync address books, it should be done automatically.
2.) Apple Address Book groups do not sync up with Zimbra. The entries in the groups are added to the main Zimbra address book, but groups are not maintained nor transfered from Zimbra to Address book. This is extremely important as it is one of Address Book's as well as Zimbra's more powerful features. If they can't talk together, I'd say the connector is not doing a complete job of syncing the data.
3.) It seems a bit strange to simply sync iCal data files with the Zimbra calendar. Wouldn't it be more efficient to house the .ics files on the Zimbra server and broadcast to/from the only version so things are more centralized. It seems like there would be less data transfer and confusion if it was central on the Zimbra server, and not constantly being transfered from the user's computer to the Zimbra server. This would also be ideal for groups of people that are all editing shared calendars.
I know this is a pretty critical posting, but I feel like there are other services out there that have already nailed a lot of this individually for Address Book and iCal (Plaxo for address book syncing, and iCal Exchange for LDAP ical broadcasting). Zimbra's interface and centrality is pretty great, so that's why I'd love to see the functionality worked out so we can continue to use programs like Address Book and iCal in full instead of being tied to a web browser.