Wore them out running for the first time today. On a scale of 1-10 on comfort right out of the box I would say a 8 just because the back did rub a bit during my 4 mile run. However, I am quite sure a couple more runs will break them in quite quickly. Ordered a half size up just so I could wear thicker socks and they fit perfect. I was shocked at how light weight and flexible the shoe is considering it's waterproof, was expecting them to be more clunky which is not the case at all! Tried them in the mud and worked out fine, haven't ran through a puddle yet so jury is still out on if they are entirely waterproof. Overall, very pleased with the shoes!!