The Apple iSync adaptor has now been published to the support portal. All Network Edition customers and trials who have support portal access may access and use the iSync adaptor. The latest version has improved integration with Entourage, see the release notes with the download for more details.
Please post any and all bugs/problems to bugzilla. Any general feedback both good and bad is encourage here on the forums. If there are other integrations or changes that would make Zimbra and Mac work better let us know!