I have been using this add - on for about 3 years or so. It has done wonders for me!. While I used it to block explicit sites and one needs to have self control to actually resist the urge to reset the add on.
Great for parents, allows them to control the media exposure early on if using a PC, 'Message from self' Feature is really good. I wrote bible verses for myslef to remind that I need to be holy and all my actions on the internet reflects my integrity to that commitment.