Rated 4 out of 5 stars

Even though I read the FAQ, I didn't understand a cookie exception had to be added for google.com. Instead of being buried on the developer's page, this info should be available on the extension's "new account" wizard.

This review is for a previous version of the add-on (2.0.5). 

Rated 2 out of 5 stars

Doesn't work with two-factor authentication. Google complains that cookies are not supported and doesn't allow you to log in.

This review is for a previous version of the add-on (2.0.5). 

Please try to do some research before posting a review and claiming something doesn't work. gContactSync supports two-factor authentication...the problem is that you have Thunderbird configured to block cookies.

See http://www.pirules.org/addons/gcontactsync/faq.php#cookies or http://pirules.org/forum/index.php?topic=619.0