Note - this review is for the walk-up sites only This is our go-to campground when we decide we want to go camping with short notice. The park itself is neither very popular nor very interesting, so there are usually still sites available for reservation only a few days before your intended camping trip. The park itself isn't that interesting, but it is worth noting that it is located across the road from New Glarus Brewery. The brewery is an easy walk or bike ride from the walk-in campsites.
We have camped at several of the walk-in sites. The sites are all located along the bike trail, and carts are available for transporting your gear which means you can bring more gear than you would bring backpacking. The walk-in sites have a good amount of space between each site, however the sites on the east side of the bike trail get less level the further you get from the parking lot. All sites are shaded and have fire pits and picnic tables. The sites on the west side of the trail are more level but closer to the trail, so you have less privacy from passers-by. Our personal favorite site is #19. It is the closest site to the parking lot on the east side of the trail, but you have to take a short foot-path off the main trail to get to the site and the site itself can't actually be seen from the trail or the parking lot. This makes it very quiet and private, but still not too far from your car. The campgrounds do have a lot of raccoons so it is nice to be within an easy walk of your vehicle if you would prefer to secure your food. Site 19 is also very level and spacious, with plenty of room for at least two good sized tents. You can hear some road noise in all of the walk-in sites due to the highway being near by, but it's buffered a bit by the woods so it is more of a white noise.
The walk-ins have a vault toilet centrally located along the trail, and it has always been clean whenever we've camped there. A water spigot is also located centrally among the walk-in sites. You can take a short hike to the park's ampitheater from the walk-in sites, but they do not have programs very often.