Skin on road in Canada for a year and a half

Like most: much improved posture, less effort, faster, no knee soreness(!)
Cautions: You have to keep at it regularly to keep your feet tough. If you run infrequently then you get trapped in the worst part of the cycle: always tender.

I struggle to find a place to treadmill on the few days a year when there's snow on the ground here. I got thrown out of my rec center and told to run in the snow because 'bare feet on the treadmill are unsafe', which is nonsense.