Shame on me for buying cheap running shoes. These were marked down 50% on Amazon, so I took a chance on them. I'd heard good things on a podcast about the spring technology, but I can't confirm or deny those claims. After just three runs (a total of 13 miles) the shoe caused bad blisters on my left heel. I tried a couple of different ways of lacing them, but it feels like part of the shoe construction, something between the lining and the outer part of the shoe, is rubbing against the lining. I'm not prone to blisters, I wore my usual socks and the shoe length seemed right, so I'm blaming the shoe rather than the fit. Comments from other reviewers about the flimsy uppers is accurate as well. Mom always said to say something nice, so...the laces stay tied.