One other work around for the iSync issue: you can import back-ups from the m600i into iCal.
more here:
http://howardforums.com/showthread.php?t=937904
How to:
On the m600i, go Calendar > More > Calendar Manager > Backup
Make sure bluetooth is switched on, and that the phone has been paired with the Mac
On the Mac, go Applications > Utilities > Bluetooth File Exchange.app
In Bluetooth File Exchange.app, go File > Browse Device > [your phone's name]
Navigate to: External D/Other/Backup/Agenda/[your calendar name].vcs
Click get
Put it somewhere memorable on the mac
On the mac, double click the .vcs file
Select a good calendar to import the data into
Still not ideal, granted, but it would fit my usage patterns reasonably well: keep travel events on the m600i, and export to dedicated mac calendar. Scribbled appointments on the m600i can be copied to the right calendar on the Mac without retyping.
Wonder whether the plug-in people can make use of the 'restore' function on the phone to get Mac -> M600i synchronisation working. Would still be a palaver, though.
MacBook Mac OS X (10.4.7)