Need testers for the Google labels feature !
here is a test version for syncing Google labels with CardBook : cardbook-55.5-tb.xpi
Note that the sync with Google takes some more times as I should wait at least 10 seconds between the labels sync and the contacts sync...
Note also for new Google CardBook address books, you were required to answer two times the same screen, this is OK as this is the same screen for two different access method on your Google contacts.
This is a REALLY tricky version, so it requires careful tests !