Better than a zoo because you are pretty much with the animals, though smaller in every aspect except the gift shop. After the wonderment of the rain forest with monkeys, alligators, and some birds flying by you, walking by you, saying hello, it gets a little slow with the more temperate climates. The other highlight is the arctic, where you'll have fun watching the penguins and puffins. My advice is to watch the penguins for as long as possible. They are really cute, and do fun things. I want to be a penguin.
It's definitely a worthy thing to do for a tourist, and even a local.