Rated 3 out of 5 stars

This was a wonderful add-on. Only now have I realised how much I depended on it! And it was totally free, which was obviously appreciated.
However, the so-called "update" has been a disaster for me and—as the reviews show—for a great many other people. My Google calendars disappeared and Thunderbird constantly froze. Even going back to version 0.32 didn't help. Luckily, I was able to restore a backup of my HDD from ten days ago, and that worked. (However, this is a pretty radical resolution for a problem caused by one TB add-on!)
Of course, the fact that we are talking about a free add-on counts: one can hardly ask for one's money back and we should definitely be grateful for the work the dev has put in for us over the years.
However, one can certainly ask why any changes were made. If it's not broken, why fix it? It was working perfectly! Was it for a university accessment? I don't know, and the dev has refused to volunteer any explanations.
What is demonstrably true is that, if there was any kind of testing, it was of very mediocre kind. The sheer volume of comments shows that the dev has no idea as to how to adquately test a piece of software. I'm afraid that if the new version was to impress his tutors, he has scored a spectacular own goal.
However, I—like so many others on these pages—really appreciated version 0.32, which never had any problems and was so essential as to have seemed built into TB (in fact, it should be!).
Could I therefore suggest a compromise? Leave version 0.32 to those happy with it, and create a fork for the soi-disant "awesome" new version 1.01.
That way, we poor mortal souls who are happy with version 0.32 will not be constantly asked to upgrade to a version that we don't want and which doesn't work, while those who wish to "live on the edge" can harmlessly indulge their kicks.
I repeat, if we are all complaining, it is because we were all using a useful piece of software provided to us without charge; so we should all appreciate what we have been given. However, I do think that the dev has a moral obligation to explain to those whose calendars have disappeared or whose TB has frozen (and who are not lucky enough to have a backup from ten days ago) how to downgrade to version 0.32 and get their calendars back. Or is this not possible?

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UPDATE
Thank you for your quick reply, which will help everybody (including myself!) to understand the reasoning behind the update. Actually, your explanation also goes a long way towards clarifying the problems in the new version. Please accept my apologies for my comments, therefore; especially as the fact that 17 Nov is just over a month away means that you really didn't have time to adequately test it before releasing it.

This review is for a previous version of the add-on (1.0.1). 

No, this wasn't for a university exam or anything. To be honest, if I could I wouldn't have touched it. Google is shutting down the API v1, which version 0.32 and below was using, on November 17th. This means I need to upgrade to v3 instead, which is what 1.0 and up uses. It was a full rewrite, so there were some minor problems. I believe the bigger amount of the problems was that with the new v3 API, I have a certain quota that eventually gets depleted. I am asking for more, but just imagine how many requests 300000 users will make in a day when each synchronization costs 2-3 requests.