Rated 5 out of 5 stars

Superb product - lost all of my Thunderbird contacts, but use Gmail, so they still existed, although without subfolders. Imported into Thunderbird as VCF, de-duped and edited 400+ contacts to 201 contacts in less than an hour. (gContactSync 3.0.x seems to broken, and Duplicate Contacts Manager filled the gap - and did much more.)

This review is for a previous version of the add-on (1.0.6).