I can't say enough good things about this park. It is HUGE, 10 acres according to the website and even that sounds understated. My puppy and I have already met all sorts of new and interesting creatures. There's a pretty good variety of terrain too. The open fields are broken up by patches of prairie grass and light woods. Most owners seem to pick up after their dogs too, its rare that I run into any messes. The park district does a good job of supplying bags and keeping the common areas clean. There's even a community bin for tennis balls and throwers that is usually pretty full. But, previous posters are correct, and they don't seem to enforce membership. Regardless, this resource is well worth the annual membership costs, and just imagine how amazing it could be if everyone did pay that fee.
I have encountered some semi-aggressive dogs, the admittedly my Whippet just runs away from them laughing. Be on alert with new dogs and be ready to jump in to rescue your pooch if need be.