Rated 2 out of 5 stars
This is the most useful plugin for Thunderbird. With it you get an almost complete calendar implementation and some kind o task management. The task manager have very basic functions and it would be nice to have something more advanced (and still lightweight) like "Get Things Gnome".
It looks however, that version 1.9.1 is abandoned, because reminders do not work since 17.0.8 and no fixes were issued. Note though, that betas of 2.x produced on regular basis.