Z-coil shoes. Are they really that good?

I would like to hear from anybody who has" z-coil "shoes. They are a new shoe with spring in the heal. Some people I know rave about them. They look like they would hurt you feet. In the 70’s the big thing was the “earth” shoe I bought a pair and could not wear them they hurt my legs and made my feet tired. Is this another fad ripoff or is it the best thing since sliced bread?