As far as attractions go, the zoo isn't terrible. Nor is it a must see. The major problem is a very understandable one. About half the animal exhibits appear empty because all the enclosures are designed to be big enough for the animals to be comfortable. Also, as the animals are not performers, they do not pose in photographic positions (i.e. you'll see a lot of animal butt). Still, on the right day it is definitely worth a visit. I would avoid hot days due to increased smell, and it is an outdoor park so rainy days might not be great either.
The petting zoo, quite frankly, was sad. they had farm animals (cows, pigs, etc) that you could get close to but not touch, and the actual petting area consisted of goats. Just goats.