I think Zoo Atlanta is over hyped compared to Atlanta proper. It is a few rockstar exhibits but not trip worthy other than Pandas. With the money that is in the Atlanta area they could have a much nicer zoo.
From some of the news posts here it sounds like they are planning to rebuild much of the zoo with a new reptile house, elephant exhibit, etc. No idea what the timescale is. It seems like the Georgia Aquarium now gets much of the attention that the Atlanta Zoo once got.