These are the most comfortable running shoes I have ever owned. I wish they existed twenty or thirty years ago, I would have saved my knees from a lot of damage. I walk barefoot whenever possible. These are the next best thing to being barefoot. I have used them on trails and on pavement and can't speak highly enough of them. 2/26/16 EDIT: There is a significant issue with this shoe. My foot is narrow and the second toe of both feet are longer than the big toe. This causes my second toes and my long third toes to make contact with the toe guard area of the upper. The nails catch on the guard, which after a few miles is painful. After 25 miles or so, a hole has been worn in the liner, making the contact worse. If you have 'Morton's Toe' - 2nd longer than 1st - I strongly advise looking at a different shoe. Another major problem is the complete lack of customer service on the part of Altra. I sent in a note about this issue to their customer service department and I have not heard one word back from them. Very disappointing.