There seem to be some huge bugs with syncing. I've been trolling the web and apparently iCal's new sync for Leopard is completely different and buggy. Also Entourage 2008 and Leopard do not get along. I'm trying to sync Entourage to iCal and Address Book and the sync eventually deleted all the iCal entries and then all the contacts on Entourage.
Also Address Book sync up to Yahoo doesn't work, it only syncs about half the contacts, so that is useless even though it is "easy":http://www.zaphu.com/2007/11/01/leopard-tip-sync-mac-address-book-via-yahoo-without-mac/ to setup, it seems to fail for folks like me with 7,000 contacts. Only 4,000 got across to Yahoo. Too back as Mac comes with a Yahoo synchronizer and also an Outlook synchronizer.
After a frustrating morning, the best solution seems to be a very manual process because of these bugs:
1. Get the Address Book up into Plaxo. Use Plaxo to generate a CSV file format that Outlook Express can import and which Outlook can import. Plaxo's Outlook synchronizer fails on my 7,200 plus contacts, so this looks the best. Also Plaxo gets very confused about calendar types. Entourage insists on creating a calendar called entourage in iCal, so on sync, you get lots of duplicate entries across categories of Work, Calendar and Entourage. Ugh!
2. Get the Addess Book up work with Plaxo, but synchronization really doesn't work. For instance, if I eliminate duplicates with Address Book (that's a great feature), when I resync with Plaxo, I get all the duplicates back again.
3. Yahoo Intellisync doesn't work with large files. When syncing up from Address Book, it only syncs about 4,000 and then quits. When I try to use Outlook plugin, it does create contacts, but they are the wrong type. It creates Note form rather than Contact form in Outlook 2003.
4. Fundamol which is what Scheduleworld uses, syncs fine upward Task, and Notes, but it says too many contacts when trying to shove 7000 contacts up there. Works well for calendars though.
There are some other interesting things to try when I get time as folks struggle to get calendars to work right. There is the iCal Server in Leopard Server. There is Gmail which now has sync to Blackberry Calendar (but not yet contacts) and also Calendar sync with Outlook (but no Mac).
Then there are the open source projects like "scheduleworld.com":http://scheduleworld.clom which runs an server for you that allows sync with Outlook (via something called the Funambol plugin) and with Google. It uses Funambol which is an open source project based on SyncML. It runs a Funambol server in the sky that is free, so you can get Outlook up there with the Funambol plugin. See "InternetDuctTape.com":http://internetducttape.com/2006/08/11/the-holy-grail-of-synchronization-how-to-synchronize-microsoft-outlook-multiple-locations-google-calendar-gmail-ipod-and-mobile-phone-with-funambol-scheduleworld/ for a hilarious explanation of how complicatin it is to get Outlok, Google, a Nokia Phone and an Ipod to have the same contacts and calendars.
"Tuaw":http://www.tuaw.com/2006/01/02/ask-tuaw-how-to-sync-between-address-book-and-gmail/ has some advice about address book on Mac to gmail contacts
There is an open source project called "opensync":http://opensync.org which is trying to do syncing as well. As well as "syncevolution":http://www.estamos.de/projects/SyncML/ndex.html which uses SyncML and Funambol.