Developer reply by Philippe V.
Rated 2 out of 5 stars
It's a really nice addon which can do a lot if you found out how it works. The categories are very nice to sort all of the contacs but after setting them a few times I give it up. They allways get deleted and I spend a lot of time for nothing. Since more than a year now it's not working.
This review is for a previous version of the add-on (26.8).this is due to the Google CardDAV API which is buggy...
To create your own collections, you must have a Mozilla Add-ons account.