Composite leak springs? Feedback needed

Hi all! What are your thoughts on composite leaf springs? I'm most concerned about them failing/breaking? I'm looking at them for the street. I posted here because I would think the most feedback would be from circle track racers? I have a buddy looking at them for his street stock as well?
I was looking at Hypercoil composite leaf springs?
http://www.hypercoils.com/leaf-springs.html
Author: Brads70