for years we talked bad about KOA, wife an i avoided them like the plague! Then we bought our current rv and got a free membership so we tried them. So far we have been happy and mostly notice they are convenient. The book is a good resource when planning a distant trip that requires a overnight stop as we have many times found a place to plug in for the night right off a highway.
Loved the KOA in Cape Hatteras, yes its an open field but a great spot. KOA in Niagara and Quebec City, great locations with tourist stuff such as tour bus pickup.
This year we are heading to hilton head from Ma, stopping overnight at a KOA in north Carolina. on the return we are stopping for a few nights at a different KOA in VA.
if you use the membership it will pay for itself, but i dont limit my campground searches to just KOA.