I was hoping someone would post a GA map, I knew I could count on you! I'm guessing you have Obama winning more rural counties because Romney is a poor fit for Georgia Republicans. I think he'll pick off a few rural counties but maybe not enough to really make a difference. If Obama improves it'll be mainly because of a better performance in metro Atlanta.
I agree on all the metro counties voting for Obama, but if I had to choose between Cobb and Gwinnett I'd say Gwinnett goes to Obama first. It's more diverse and its white population is declining at a faster rate.