We have been zoo members for about 4 years. While we love seeing the animals, I am disappointed by the expansions and higher costs. They keep adding attractions - a luge ride, an improved train, etc. I don't think a zoo needs all of those things ,when you are there to see the animals! The cost is prohibitive if you are going to take a large family, but if you can afford an annual pass, it's worth it!
The aquarium is great for the summer, and we also like to feed the lorries.