I've been a Nike Free wearer for the last 3 years, but have recently switched to wearing Air Rifts for both training and racing and was wondering if anyone else has had success with them. They appear to be quite built up at the heel but in fact the foot sits way down inside the shoe making them pretty flat. They seem much more like a barefoot shoe than the Free and are a lot lighter. They also have the almost unique advantage of having been on the market unchanged for the last 11 years and show no signs of being discontinued. Any thoughts?