I've never used one, but they always look like a gimick to me because of the price (both these and RidersRasp too).
Not to say they might not work lovely. I've never used one so I don't know. But they are priced higher than a farrier's rasp. Which is two sided and what professional farriers use. So why not use that?
Maybe because I've taken farrier science I am used to a standard rasp. I don't remember the last time I've skinned myself. Make sure you have a rasp handle and use two hands...one on each end of the rasp. Works pretty well.
So yeah, they might work great, but I almost see these funny looking types of rasps as taking advantage of horse owners who don't know any better.