In reality I know from past experience that Google is perfectly capable of screwing up synchronization time and again, and that they don't admit their problems.
So it's good to see Spanning Sync fighting back with a point-by-point attack on Google's sync solution. For example:
Spanning Sync Blog: Google's "Appreciated Gesture" Drives Record Sales of Spanning Sync:Ok, that's a wee bit of a limitation! I didn't read that anywhere else, but I believe it. I'm not willing to experiment with CalDAV sync, I really don't trust Google's ability to do this stuff.
... Calendars synchronized using CalDAV become read-only on iPhone. One of our biggest customers is in the process of rolling out 700 iPhones and 200 iPod touches. This lack of iPhone compatibility makes Google's CalDAV solution a non-starter for them, and for anyone else looking for bidirectional sync between iPhone and Google Calendar."
I think what most of us want is synchronization between the iPhone calendar app and Google Calendar; we could leave iCal out of the picture. Unfortunately it's not clear if Apple will allow such an app to be deployed.
Please Google Android, Palm Centro and Microsoft ... be successful. We iPhone users need your competition. In the meantime, I'm thinking of trying BusySync and Spanning Sync again.