Needs improvement, really a good google to apple addressbook sync.

does not seem to merge contacts well. e.g. if i have a contact of a given name, and later add an email to it, the second email is not added to the other record. basically any change to an existing record never seems to get shoved over. I need to delete it in my mac addressbook and then have it sync from google again. This is best, because deleting contacts in google causes linked accounts such as google chat and google+ to be deleted of course.

does not seem to synchronize picture / avatars. e.g. a contact in google with a picture, the picture is not on the newly created contact in apple address book.

when i merge from apple address book to google, sometimes i see it creates additional group in the google contacts interface, (e.g. "Family", "Coworkers" etc. when there is clearly already the group there. instead of just stufing them into the existing group.

So basically, it seems to work best if
- you like to use your google contact list as the master, and do not have any manually added stuff to your apple contacts.
- you do the delete of target contact list and synchronize from google to apple book, so that the google master list gets applied every time to capture changes to existing records.
- you dont mind having no avatar picture in your apple contacts, because you would need to manually applying the picture icons to your apple contacts after synchronizing them from google. but the delete on sync makes them all go away agin.

travishein about Contacts Sync for Google Gmail, v3