If you heard about the site on Clark Howard, so did I; however, I used the phone number, instead of the website, to opt out. You have a choice of a 5-year opt out or a permanent opt out. They will send you a form in the mail if you want the permanent opt out of credit card offers and insurance offers. I just received mine in the mail last week. The 5-year opt out is immediate when you call or log on, but the permanent opt out is only put into place once you send back the signed form.
I am hanging on to the form since it's forever and I am not sure I really want to permanently remove myself from "firm offers of credit or insurance".
Be advised that, according to the opt out form, "you may continue to receive offers from sources that do not use Consumer Credit Reporting Companies to compile their lists".
I hope this helps anyone with questions.