Most recent ones should be, (barring Treo 700w).
I have a Zire 72 and it works absolutely fine through Palm Desktop, but I would prefer to use it through iSync for calendars. However, it doesn't recognise the Palm software being on there and so iSync does not work for me.
As long as you are happy to sync through Palm Desktop, you should be fine with all the current range, (again, except the Windows based Treo 700w).