I've been running in these for over two weeks now and am starting to feel sore in places that I never did before with regular running shoes.  The light-weight protection is great and it feels very natural once you get used to them.  It took a couple of break in days before I could run over three miles but now I feel great! I normally wear a 10.5 mens but I wanted a snug fit so I ordered down and they fit perfectly.  They even fit well with the five-finger socks that I use.  I recommend these over the Vibrams for weight savings and shoe flexibility.