If I can remember, the Bluetooth implementation seems to be somewhat lacking on the Mac side-that is, Mac OS seems to not support all the profiles allowing full transfer of files between the two devices. I had a K750i back in the day, and remember that I could only sync one way-bummer!
I ended up buying an external card reader for my micro SD card, and drag-n-drop downloading to that card on the Mac, to get my tunes on it…now that may all have changed since then (newer Mac OS Leopard, firmware/model updates with your phone), but if you want to be completely sure, look up Bluetooth compatibility on Apple’s support knowledge base.
Alternately, you can research a sync software program, such as this one I found on a tech forum:
http://www.versiontracker.com/dyn/moreinfo/macosx/30274&mode=feedback?tag=forums06;posts
The software plug-in costs about $3 but allows iSync to see your phone for address book/iCal support. I think that’s all via USB cable though…so on the issue of BT over-the-air sync, don’t know the answer to that one.