It kind of works, most of the time. On other occasions you'll get meeting reminders you can't dismiss, event cancellations which stack a new crossed out date on the list for every "update" click, events where you can't set attendance, and the annoying "you clicked dismiss, would you like to submit the modified event to the server" dialog. And that's on a good day :-(

There's lots of outstanding bugs unfortunately.

See https://bugzilla.mozilla.org/show_bug.cgi?id=1314185 - earliest dependent bug is 8 years old.

It's never worked well for me, e.g., when responding to third party calendar invitations, when moving meetings with others, when using two-factor authentication, when adding contacts on multiple devices.

Both of those add-ons have always been clunky and brittle for me. They have caused me to miss appointments and have also occasionally messed up my contact data.

I would never, ever use these add-ons for work.

See viraptor's comment for links to reported bugs: https://news.ycombinator.com/item?id=16340039

The entire email client froze up the very first time I tried to sync my Google calendar via Lightning. On subsequent syncs the UI only became unresponsive for several seconds. I dunno why sync was running on the UI thread, but it made Thunderbird nearly unusable until I disabled it.

Used to use these in work until our internal security team banned all desktop clients. "Just works" is incredibly charitable.