If we had to pay to get in, the place would merit only 3 stars. But the wifey and I visited during Kids' Week (or something like that). So we got in for free, as did everybody else. Boy, was it crowded. There were so many parents and kids in the Insectarium that the moment we stepped in, we got outta there. It was basically a human sauna.
The Chineses and Japanese sections were the best part of the park. They did a nice job with that. Also, check out the tri-wing greenhouse just before the main entrance. There was a huge assortment of tropical trees, and other foreign botanical plants. The collection of bonzai mini-trees and the accompanying detailed explanations were cool.
Basically, try to visit either during a free weekend or with a free pass.