This is a very large state park located halfway between Mineral Point and New Glarus, both nice visiting destinations in their own right.
It has a large lake with three boat launches, a main one with a motor ramp, a canoe launch near the marshy end, and a fishing pier. There's also a boat rental place run by the nearby Cork Down Saloon. There are no boat-in or lake accessible campsites however.
 The campground is up a long 30 degree hill across from the main launch and Beach/ main picnic area. The sites are more secluded from each other than you'll find at most parks , which is very nice. Beware that some sites are so secluded that they are bi-level. That is, parking pad and then step(s) down to the site. Be sure to check the photos provided when reserving.  There are very nice walk-in sites, but no carts are provided.
the facilities are clean, but there's only one building with running water and showers. Water throughout has a mild iron taste.
There's no playground in the camp area, it's located in a picnic area near the canoe launch that you pass as you com in. Not walking distance, remember the big hill.
 There's an Ice Cream/concession at the east end of the lake with limited hours. Beyond that is the Cork Down Saloon, just outside the secondary entrance to the park. It's your closest option to eat out. Also there is the private Chalet campground (see others for a review) Neither has a view of the lake as they are below the Dam.
A fun place to visit in the area is the Toy Train Barn Museum in Argyle, indoors if you have a rainy day.