Apparently Plaxo only syncs with Google Calendar about once an hour, which is longer than I was prepared to wait. I'm after something that syncs within 15 minutes so I can jump between computers and not have to wait long for my calendar to catch up.
Of course there was the option of abandoning Google and just sticking with the Plaxo calendar, but I didn't like the fact it was limited to displaying a seven hour window because of the rest of the junk on the page. I'd also rather stick with Google because I already use it for so many things, including sharing calendars, and it's easier to stay put (which is the thinking behind companies like Google offering so many services).
Next on my list was BusySync, which sells for $US20 ($US25 once v2.0 goes out of beta). Here I struck gold. As well as syncing with Google Calendar, BusySync also lets you share iCal calendars between Macs over the internet or your local network. Admittedly I only have a MacBook, but I'm very happy with it so far and I'm sure it won't be my last Mac.
BusySync can handle multiple calendars, letting you schedule regular syncs and track their progress. It also makes daily backups of your calendar, storing the last 10 and allowing you to restore your calendar should disaster strike. As well as sync with Google calendars, BusySync lets you publish your iCal calendar for others to see and subscribe to other people's calendars.
BusySync easily passed my duplicates test, although its shortcoming is that it adds your iCal calendar to your Google Calendar as an extra calendar rather than synchronising with your default Google Calendar. This is annoying because whenever you go to create an appointment in Google Calendar you have to remember to switch to your default calendar. The way around this is to export your iCal calendar as an .ICS file, upload this data into Google's default calendar, delete your iCal calendar and then re-sync, after which the default Google calendar appears in iCal. It sounds complicated but it's a quick and easy process.
I'd say BusySync's reasonable pricing, extra features (such as online backup) and reliability make it the pick of the bunch to marry iCal and Google Calendar - until they day comes when Google's online calendar matches the features of a desktop app.
The Road to Leopard: Amazon S3 and Jungle Disk deliver me from the backup wilderness