I have a Nokia 7610. I have a Mac mini, with internal bluetooth and Tiger. I can sync them, and all seems well. Contacts get across fine, and a fair few appointments get over as well...but not all. I cannot discern any rhyme or reason behind the selection of successful appointments. I have three calendars: one is created by me, one Birthdays from Address Book, and one subscribed from apple.com. Of these, some appointments from each get synced, with a range of different characters used in their names. I have enough free memory on the phone. I have disabled/exited/uninstalled 3rd-party apps to do with this: I used to use ActiveDesk, but uninstalled it after it made things unreliable, and have reset things since, and I now use AquaCalendar but keep it not running during sync. Nothing shows up in Console.app. No errors are reported either end. iSync is told to sync everything.
If anyone has any insight, please share it before I turn slightly insane.