I have a lot of trouble with iSync (to my Treo) and .Mac sync. A few weeks ago, it was generating bogus complaints and bloating ~/Library/Application Support/SyncServices (up to 9gb in a single HotSync, which ran the PowerBook's hard disk out of space). I eventually cleared that one.

I had to abort a HotSync a couple days ago. Yesterday, Palm syncs (which I do twice per day or more, to get fresh plucker content) stopped updating my calendar. I cleared iSync's state, cleared .Mac's state, completely erased my Treo (scary, when the master data on the PowerBook might have been [and in the end actually was] corrupt), yada yada yada. I got different (related) errors, but nothing actually did the trick, until I backed up my data from iCal and reloaded it (luckily, this apparently blew away the corruption). Even this was fraught. I tested by loading it on another system -- trying to make sure the export was good, as I didn't trust the source. But when I attempted to open the iCal backup on the other system, iCal just spun and spun but never seemed to get anywhere. Eventually I realized it was calculating the disk size on the iCal backup. iCal backups are actually packages (folders), and it was taking much longer than it should have to total up the size of the folder, during which iCal was unresponsive (I actually force quit it a few times before I figured out what was going on).

Lesson for Apple is (aside from please fix synching in Leopard!!!): when complaining about a database synchronization error, identify the database you're complaining about! The iSync conduit was spewing errors about updating a specific record number. Of course, I have no reference for what that record number means. Had it mentioned that this was a problem in the iCal database, not the Palm DB or the "Truth database" (on iDisk), I could have saved hours and skipped erasing the Treo.

Another bug, just confirmed and reported. In the .Mac sync reconciliation dialog, I can't activate the "default" (blue throbbing) button with Return/Enter; it gets passed through to the window behind the dialog, although I can change the dialog's pop-up menu from the keyboard.

As it turned out, i started this posting prematurely last month. iSync was still corrupted. I had to wipe my Palm a couple more times, delete all my .Mac sync clients a couple more times, and even enable synching from iCal's & Address Book's preferences because System Preferences:.Mac:Sync wasn't usable -- it would just spin forever, never letting me actually click on the check-boxes to enable synching or specific types of data.

A week later, that part of System Preferences works again, and I have no idea why.

I also don't know how much longer it will continue to work. I was very intrigued by SyncTogether, until I discovered it just uses the same Sync Services infrastructure that keeps breaking so badly on me. I basically pay $100/year for .Mac sync, since I don't use their promo software and I run a more reliable mail server myself (on Apple hardware and software, no less!), so I'd love to find a cheaper alternative, but it's not clear if SyncTogether would really be cheaper (depends on upgrade schedule and pricing, and how many machines, and would require me to poke additional holes in my firewall). Unless and until Apple's syching gets stable, it doesn't make sense to invest more in it than I already am. Additionally, I don't know how soon Mark/Space will have Leopard support.