I love these shoes. I went from a non-carbon soled shoe to these stiffer, carbon composite soles and most definitely feel a difference in pedaling, especially up hills. It feels like the stiffer sole translates into much more power when muscling up the steep hills. The shoe is very comfortable and the size chart was spot on for me. I would consider myself an avid, mostly recreational cyclist and I do a variety of riding from distance rides of 50 miles with some time trial racing thrown in, mainly to see how I measure up. I'm anxious to do these events in my new Sidi shoes. They are a very light, comfortable, productive shoe. Highly recommend.