I'd never worn shoes like this before; I'd never heard of them. The first time I wore kyBoot shoes, it was extremely tough for me to stand in the shoes while singing. I needed a moment off to stand on the hard ground. The next day my calf muscles ached. But it kept getting better over time. I got used to it more and the shoes got softer. Now it feels really pleasant singing on that surface. You bounce about a bit, which is very pleasant.
Because your body is more active, it lifts your mood. I could certainly imagine that it helps your voice carry better.
We were at a regional music festival where we wore the shoes from morning to night. The next day, my feet were fine. I had no pain at all. My feet always ached with my old shoes. I would always have to Cool my feet down the next day. I had no problem whatsoever with the kyBoots. It was very positive for me.