Rated 5 out of 5 stars

It's the best PIM out there. For me Thunderbird IS Lightning.. don't care for the mail client as much. Please make a proper mobile equivalent in the new Firefox OS to sync properly with the desktop version (tasks, contacts etc.). Thank you & Congratz for such a good job

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

As long as you have a caldav server (Google, Yahoo, Custom), you can already sync your events and tasks with the firefox os calendar application. Contacts should work with carddav, but you need an extension to make contacts work with carddav in Thunderbird.