Again, Greenville Zoo is a very clean, well cared for zoo... but with the few animals they have, keeping the place maintained is a must... it's one of the attractions itself!
I purchased the anual pass in order to have a place to take my two year old niece a few times a week without dealing with the "big kids" in Cleveland park, while having a good place to exercise. As another poster mentioned, the hills will kick your butt!