If I could count all the times I was caught with pron in my history and cookies.....heh
I never had restrictions on what I could/could not view on the internet. When I was caught with pron, I was lectured, then I did it again, and I was lectured again, and so on. Life moved on, and everybody is doing great these days.
What exactly are you trying to keep your kids from viewing? If they arent exposed to it in this way, they'll find another way.
On another note, I suppose the risks of the internet have changed for youths comparing my childhood to today's children. When I was a young teenager, there werent many things on the internet to be worried about. Today, meeting people online is extremely popular among teenagers, and they can be easily taken advantage of. If thats what you're worried about, I dont think you should purchase software to do a job that you as a parent should be doing; which is to parent your kids and teach them right from wrong. If you are worried about pron, thats just ridiculous IMO.