I posted a blog on the Peti-Paws, and it took about a week for Joey to get use to the noise. I went really slow, and the first few days just turned it on for a few seconds, and gave him a treat, later actually letting him feel the vibrations. Here's a detailed account for those interested.
http://www.yorkietalk.com/forums/blo...ally-work.html
I'm glad I bought it because I found that his nails grow at different rates, and only a couple on the front paws really need regular clipping, I guess he keeps the rest of his worn down naturally.