I had never heard of these, but after looking them up, I don't really get it.
The first testimonial on the website is about how the person's legs were sore after wearing them for a few days. They use that as a good thing to show that they are giving you a workout. So I can understand buying them for non-disney use to work your leg muscles and burn more calories.
But walking around disney is tiring enough as it is, so why would you want to wear shoes that make your legs work harder?