As a paper carrier, I actually use this app, and it has come in handy. The paper I deliver doesn't usually do checks without me asking, so I take it upon myself - and one of my ex-customers was, in fact, a child molester.
You can never be too careful. They've done horrendous acts, and in my opinion, the point of being on this list isn't to destroy the privacy, it's to protect the children around them. Use it to make sure that house your looking forward to buying doesn't have a sicko living next to it.