Flawless, and fast, as in 'it just works' with Google calendar. SpanningSync looks good, and they are certainly trying hard enough. But it often stalls, or does just a partial sync (I typically have about 12 calendars active), or syncs only in one direction. They blame it on Google protocols, but BusySync sidesteps all that, and is very quick at automatically updating. No hiccups whatever. The odd thing about BusySync documentation is that it appears as if the .prefPane merely automates iCal's publish and subscribe protocols. But all one has to do is publish to Google calendar from iCal (via BusySync), and then a change at _either_ end will update on the other. So after a couple of days with BusySync I am about to break a personal rule not to buy software until the full trial period has been exercised. Well, maybe a few more days. And hoping that BusySync will in future extend to synchronizing Address Book with Google contacts . . . .