Rated 5 out of 5 stars

Using 4.0rc5 and it works very well. The only issue is that in earlier versions when synchronizing small changes, e.g. deleting single contact, it took couple of seconds, but now it synchronizes the whole group which has been "touched". And for address books with 1000+ contacts it takes 5-10 minutes.

This review is for a previous version of the add-on (0.3.6). 

gContactSync only synchronizes contacts whose last modified dates have been changed. Thunderbird sometimes changes contacts in the background, such as whenever you receive an e-mail from them or send them an e-mail, for example. Version 0.5 will only sync contacts if one of the synchronized fields changed since the last sync.

If you can recreate this in a short period of time during which you don't send or receive any e-mail please send me a log.

Josh