As noted, it certainly doesn't make the job effortless but it makes nearly any tire/rim combination possible. I've used mine to install very tight fitting tires that were much too hard to fit by hand and endangered standard tire levers. It works very well.

BTW, I've noticed that once you coerce a tire onto a rim the first time, removing and replacing it afterward is quite a bit easier. Tires that required the Kool Stop to install them the first time could be reinstalled with ordinary tire levers afterward so roadside repairs were not a hassle.