I've been using the public beta of iSync to sync my Palm VIIx to Address Book, iCal, and Palm Desktop under OS X 10.2.1. Most of the time things go pretty well (albeit abysmally slowly), but every once in a while iSync spazzes out and either deletes all the calendar entries in iCal, or on the Palm, or the same thing with the ToDo list. It seems pretty random when this happens. I've cured it before (when it just deletes record off the computer) by removing all the iCal files from the ~/library, and resyncing. It's a bit more difficult to recover when it deletes records off the Palm AND the computer. Has anyone had similar difficulties?
Admittedly, I also sync the Palm to my PC (yes, running Windows and everything) at work, but that's syncing only to Palm Desktop, obviously. Apple says you shouldn't sync to more than one computer unless you're using .Mac, but that's not going to work on a PC anyway, so if you need to sync cross-platform, you're outta luck, I guess.