Rated 5 out of 5 stars

At fist, I encountered the same problems described in the previous comment titled "Broken".
Thunderbird froze after adding a Google Calender.
After killing the Thunderbird process and restarting (in normal mode), it seemed to work fine.
However, Thundebird froze again when I added my first test event to the calendar.
After killing the Thunderbird process once or twice, it finally seems to work fine.

I am not sure why I encountered these issues at first (maybe this is the "issues with Google's API access rules" mentioned in the add-on's description?), but they appear to be gone now: I can read and write events to my Google calendar as expected.

Haven't tried tasks which are not yet supported according to the description.

My system specs:
* Windows Vista, SP 1
* Thunderbird 24.0
* Lightning 2.6
* Provider for Google Calendar 0.25

This review is for a previous version of the add-on (0.25).