I've been running and Saucony iso has been winning for years and I'm dying to try these new models. Unfortunately, to my dismay, these particular models have a significantly redesigned toe box. This marathon workout resulted in lots of blisters, one blister that was left with blood, etc. I will continue to wear them until they die and I hope new versions of the calluses will form and protect my feet, but if you spend the prices up Saucony I expect significantly different results. In terms of comfort and weight, they are good. Still undecided on longevity.