I'm not sure what you mean when you say it was your "… understanding that iSync in OS 10.4.5 resolved many issues that Missing Sync did before." I cannot thing of a single such resolved issue.
While the release of iSync [and the embedded iSync Palm Conduit] with Mac OS X 10.4 shifted it from essentially a stand-alone application to a component which uses the SyncServices framework, it resolved NOTHING with regard to its long-standing issues, and introduced several more.
• it does not recognize group and category labels
• it synchronizes address only if they are labeled home
• it has no provision to synchronize memos
• it often creates an Unfiled calendar in iCal [a new issue with iSync 2]
• it does not properly synchronize Address Book-generated birthdays which appear in iCal [also new with iSync 2]
• except for an initial synchronization event, 'synchronize' is the only available option
• you can no longer immediately reverse the effects of a synchronization event [again, this is new with iSync 2]
These are just a few of the issues carried forward to—or introduced with—and still present in iSync 2. It is less stable, predictable or reliable than earlier releases. I am on record as an intensive user of Apple technology for more than two decades as having said that the current release of iSync, taken in total, is probably the worst technology release I have ever seen from Apple. And, I sincerely mean that.
The SyncServices framework is a great leap forward, but iSync 2 is an abysmal application, made far worse by the antiquated iSync Palm Conduit.
It is worth pointing out that the installation and use of the Missing Sync for Palm OS under Mac OS X 10.4 or later does not add to your collection of software, it actually reduces it by replacing the HotSync Manager and iSync.