On a recent trip to the UP Michigan, we stayed at 2 different KOA's in Wisconsin. Both were nice, clean and everything you'd expect from a KOA. The one we really liked was in Hancock WI, which looked very new, with exceptionally nice facilities. The log cabin lodge was well done, and a nice facility. The woman at the lodge, I assume owner(?) was very friendly, and had a person take us to the site. From what we could tell, all the sites were pull-thru, with lots of room between sites, with trees, and space at the end for your vehicle(s). Would highly recommend it.
The Madison KOA, actually in De Forest WI, was also nice, clean, but the spaces were fairly small, and no trees. Facilities were good too.
Overall, we used these sites as one night stops on our longer trip, so didn't spend more than one night. The one in DeForest WI is just a few miles down the road from a Camping World, if you need any anything.