Hmmmm... Like any tool, this can be mis-used as much as anything else, or worse.
Right off the bat, I can see X number of people trying to put an undersized dog nail in an oversized hole, holding it for 1/2 second too long, etc. Remember, this is a non-failsafe (no matter what the cheesefomercial says), high speed, power grinding tool to be used on our pet's sensitive tootsies, which comes with all potential pitfalls associated with it.
A simple, high quality (do your research) snipper used with proper technique, and frequency (and as Numbers said, a reward at the end) will give best results.
Gotta' love how the infomercial shows no dogs freaking out at the sound (actually, it doesn't even let you hear the sound), and/or vibration. Yeah, let 'em try this thing on my aunt's Shepherd... someone's gonna' be missing a hand.