Rated 3 out of 5 stars

If Google is the prime source for your contact info and all you want is to have an updateable clone in Thunderbird, then this extension works very well indeed.

Unfortunately it isn't so good if you want to work the other way around. Thunderbird phone number can move mysteriously between types (so that fax number can become a work number, say), and the structured mail addresses in Thunderbird can be replaced by a formatted block of text. For someone who wants Google to be a synced copy of the Thunderbird master version this is crying out for the option to keep the Thunderbird fields intact, and manage the Google contacts fields to fit - then it really would be great!

This review is for a previous version of the add-on (0.2.12).