We did it a few years ago and was great! Only thing is don't rely on the photographer they send along with you for photos. My husband decided not to take many pics from our own camera and just buy the ones we liked at the end of the day. Most photos taken by the "professional guy" were fuzzy or poor quality.
We got to hold a number of species ie milk snakes, baby tortoises, fijian iguanas, frilly, and got to go in the paddock with the giant tortoises, which was cool! Also saw a number of eyelash vipers being fed! We will be doing it again at some stage, though I think it is more expensive now than it was then.
There is an old thread that I made shortly after we did it with some of the pics of the day.