I have used DiskTracker for years now. It is simple, easy to use and, until recently, was pretty much bullet proof. Snow Leopard threw in some unexpected kinks, but the developer was very responsive to inquiry, got right on it, and we're now back in business. I don't agree with the previous reviewer that the interface needs to become more glitzy. When something works so well for the purpose intended and doesn't require an extensive manual to figure it out, why mess with it? Highly recommended.