If you are a member of an affiliate zoo, ask for a Zoo Member Discount; also ask at your affiliate zoo before you go for possible free tickets. Atlanta Zoo is affiliated and probably most of the big zoos are also.
The zoo is a good size zoo. They went to great ends to make sure that you are surrounded by beauty everywhere you go. I found it nice to just wander around through all the nooks and crannies. We had fun in the bird aviaries, as the birds there are NOT shy. We had several close encounters with the very friendly feathered friends.
You have to wait in line to see the pandas and it gets over so quick that it is over shadowed by the other areas. They don't lack humor, especially by the rhinos. It seems that they have a rather large "back blast" area that you need to be careful of. Make sure to take a ride on the aerial buckets as you get a great view of the area. They do have a really large variety of plants and animals. I was surprised by the plants. . . I expected the animal part, but the plant variation surprised me.
If you are looking for a good workout, this may do the trick for you also. There are a lot of hills to walk up and down. If you don't want have as much exercise there are trams that go through the park.
The zoo employees are extremely nice and informative. Talk to them! They know quite a bit about the areas they work in. I was fascinated by the dwarf deer and it happened that one of the guys was there working in their area and was able to tell us all sorts of trivia about them.
The food wasn't bad either.