Rated 2 out of 5 stars

I really want this to work, but I have contact data getting mismatched to other contacts, those mismatches being synced back up to Google. Now my caller ID (using google contacts) and multiple IMAP accounts (also using google contacts) are wrong across multiple types of service. I don't have time to troubleshoot what should 'just work'.

This review is for a previous version of the add-on (3.0.0). 

Do you have multiple contacts with the same e-mail address in a TB mailing list? If so, Thunderbird will munge the contacts together. Unfortunately I can't do much about this without a TB address book rewrite. If you can't resolve these duplicates (use Google's contacts interface) you should sync each group with a different address book.