Rated 2 out of 5 stars

Don't know why, but this add-on specifically managed to remove the text for 'File', 'Edit', 'View' and some of the items in those menus themselves in TB 3.0. Removing it cleared up the problem. Also, it doesn't seem to support having multiple address books and keeping them separated by email address; it just wants to merge them all into one big happy address book. When handling personal and business emails through one interface, this is not a benefit.

This review is for a previous version of the add-on (0.8.13). 

options for sync with multiple accounts

Ssurgul, if you want to sync multiple accounts, you can choose to either:
a) sync them all together by syncing each one with personal address book or
b) keep them separate by syncing each one with an addressbook named after the account email address
See: http://zindus.com/faq-thunderbird-google

The File/Edit issue is a Lightning bug, fixed in Thunderbird 3.0.1, see:
https://bugzilla.mozilla.org/show_bug.cgi?id=398702