Disgraceful Rated 2 out of 5 stars

When it works, Lightning is very useful, and completes all the tasks necessary for a standard calendar within an email program. Unfortunately, it almost never works, especially when Thunderbird updates. It slows Thunderbird down, freezes Thunderbird regularly (especially when Lightning has an event alarm), or crashes the Thunderbird entirely. Seriously, don't waste your time. Just get the "Google Calendar Tab" app instead - it's not as feature rich, but it at least won't give you the grief Lightning does.

This review is for a previous version of the add-on (1.9).