Rated 3 out of 5 stars

It would seem it is possible to sync Google Calendar with Thunderbird. You WILL require the Lightning Add-On. It sure would have been nice if someone published the answer instead of the vague "I know but you don't" reply...
So here it is:

http://www.google.com/support/calendar/bin/answer.py?answer=99358#sunbird

Substitute Thunderbird for Sunbird, and the directions work fine.

PS. Save your $10 Provider support fee for a beer.

This review is for a previous version of the add-on (0.6b1).