I bought a pair of black mesh.  They were so comfortable right out of the box.  I got half a size larger based on the reviewers opinion.  I can wear thick athletic socks with these.  They are almost weightless and not binding.  If your feet aren't used to putting on mileage you may get tired and sore feet wearing these.  If your feet have been trained to cover distance, you'd love not having to log weighty sneakers around.  I have been wearing these day after days because they are that comfortable.