I'm loving this!
As a runner, I deal with calluses all the time.  They build up pretty quickly and can become quite uncomfortable.  I've been using this file for a few weeks now and it's has does an excellent job of helping me keep my calluses in check.  I use it on the balls of my feet and my heals.  It can remove a good amount of skin without irritation.  The handle makes it easy to use and reach all parts of my foot with ease.
Rating: 5 stars