Is this a safe thing to do or will things get messed up? I'm using a BES and doing over-the-air sync of contacts and calendars... can I also sync with my Mac using PocketMac (with iCal and Address Book)?

This works just fine. Why don't you turn off OTA address sync first, then sync your Mac with the BlackBerry and check out the results just to be sure. After everything looks ok, turn OTA sync back on. You can turn it off and on in the Options menu from Addressbook. The only issue I've had with PocketMac is syncing Nextel radio numbers. PocketMac maps the radio number to "Home 2" in AddressBook, and messes it all up. Also, the current version of PocketMac does not sync both work and home info, where as OS 4 on the BlackBerry can now support it.

Don't forget AddressBook and Mail will sync to your Exchange server just fine too...

Thanks jcalchi. Seems PocketMac won't sync over Bluetooth so I'll have to bring my cable from home tomorrow and try it out.

And I know AddressBook and Mail sync with Exchange, but unfortunately it's iCal that I'm really interested in - everybody else in the office is on a Mac and using iCal, and I need to be able to share calendar information with them.

Check out snerdware.com. Thier product does a great job of syncing iCal with the Exchange Server. It's worth the money.