Saw this on an RSS feed, downloaded, installed and had new icons in the space of 2 minutes. Easiest app I think I've ever used. I was using Candy Bar, but didn't really need 90% of it's functionality. This app also creates decent size ICNS images. Transparency is correct (from Fireworks PNG files). I'm happily going to pay the money to unlock the favicon features (I know there are free online apps for this, but I'm a sucker for helping out developers of inexpensive, quality software).

Can't comment on stability yet - too early to know - but I'm very impressed so far.