Have to disagree Andy. It's not like it's locked the spring up. I've installed them on mine right up near the top of the spring as recommended by the manufacturers, so it's right up there sitting between the coil and the contact plate of the underside of the car. I will try to get a photo loaded of them on my car. The vast majority of the spring is free to compress as it would normally. Effectively it's just raised the ride height and not altered the compression rate of the spring.
I think they're great, but if you don't like them, don't buy them.