Rated 4 out of 5 stars

Really useful add-on! Been using it for years. And it seems that performance and stability has improved over the years.

Regarding problems with 1.0.X versions. Version 1.0.2 seems to make the calenders working normally again.

I'm using a master password, and in the 1.0.X version I get a bunch of master-password login dialogs (one for each calender) when starting Thunderbird - annoying! Previously I only got two, which was acceptable.

This review is for a previous version of the add-on (1.0.2). 

Please take a look at the Startupmaster extension. This is mostly a platform issue, which will likely be solved in a later version of Thunderbird.