I've had my Treo 650 from AT&T/Cingular for about two weeks now and I absolutely love it! I also have a 12" Powerbook 1gHZ running 10.3.8. The Treo syncs via bluetooth perfectly with Mac OS X. However, it took a little bit of work in the beginning but now it syncs fine. The bluetooth syncs are a little slow (about 5 to 6 minutes) but not a big deal to me. If I'm installing a bunch of apps then I'll plug in the USB cable. iCal and Address Book both sync fine as well. My only complaint is that I wish you could mount the SD card in the Treo on your desktop, but I guess that's a Palm/Mac issue in general. I heard that Missing Sync resolves this problem. I also cannot browse my Treo via blueooth. At each sync it will automatically download any pictures or videos that I took with my Treo to a folder on my Mac.
I also have a Garmin iQue3600 and that syncs fine with my powerbook too. I have it setup on a separate Palm profile and iSync does a great job managing everything.
I personally think that the $40 that Missing Sync charges is a bit too steep for my needs. Unless you really want your SD Card mounted (I just use a memory card reader), or want your Entourage stuff synced, then you're fine without Missing Sync.
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