Not stable yet. good try. Rated 2 out of 5 stars

not pleased, I wrote the prior review "Thank you, Great Add-on" before I started running into problems. I have 3.1.9 of Thunderbird, don't know if other versions affected. Somehow in the sync with google calendar this app screws up something. I've now lost access to 2 newly created calendars in google. Google error message, "this calendar did not load" i.e. it's gone? Uninstalling before it breaks any other calendar. Hope you all have more luck.

This review is for a previous version of the add-on (3.5). 

Thank you, Great Add-on Rated 5 out of 5 stars

have been using "lightning" extension for several years with "provider for google calendar" extension but was never happy. I now prefer this for managing my calendar. Why? 1. Lightning does not let you customize number of viewable calendar days. It just lets you see one day or a week. This is important if your actively planning your work schedule by moving tasks around. 2. Even though google calendars can be added in lightning it takes longer and you still have to go to Google to manage calendar sharing etc. Issues: not all Google calendar features can be accessed via this app such as "show only this calendar" and changing color of a calendar although these sync after changing them in Google. Other than that this is finally the best solution for using Google calendar as a task manager which is really the best use of a calendar after all. For example: Top of the calendar I have "All day events" from my "daily work" calendar which I use solely for tasks. then I add specific times for doing those tasks as events which can easily be moved around.
Thanks again to the developer.

This review is for a previous version of the add-on (3.5).