So far it's syncing the messages sent and received via Adium. They show up in google+, although they're not automatically marked as read (though I've not yet received the google+ update). Images and hangout invites are not synced. I have yet to attempt a group chat.
UPDATE: Photos will show in the messenger, or send you a link to a google+ page if you're on gchat.
UPDATE: Photos will show in the messenger, or send you a link to a google+ page if you're on gchat.