Well I just picked up one today to try out.
It doesn't seem to bother the dogs much but I myself have to get use to it. It will take some practice for me to get it right. The sound of the nail hitting it kinda bugs me but doesn't bother the dogs at all. I think I may try it without the orange cap because I kept hitting the nail on the end of the thing which they did not like.
My only complaint would be that it takes so long to do. I am use to cutting nails and being done and over with it in two minutes. This takes longer as you can only do it for 3-5 seconds and it doesn't take off too much in that time.
I think I will mostly use it in addition to the nail clippers. I will clip off so much and make the nail smooth and round by finishing with the pedipaws.
In conclusion, I am happy so far with it, it will just take me some time to get use to it.