Rated 5 out of 5 stars

This module works perfectly for me. When it doesn't, (nothing appearing in both Agenda and tasks from Google) there is a trick to do :
Close thunderbird
Go to your profile folder (usually it's there : C:\Users\YourUserFolder\AppData\Roaming\Thunderbird\Profiles\YourThunderbirdProfile.default).
In that profile folder, open the folder named "calendar-data", delete everything in it (cache.sqlite something and deleted.sqlite) except the "backup" folder.
Close the open folders.
Restart Thunderbird and everything should be working fine.

This review is for a previous version of the add-on (1.0.4).