As the first online course I've ever taken, I can say without doubt that it has been a tremendously great experience. I know that a lot people that took Intro to Number Theory were still in grade school, but taking it as a senior in high school, I still feel challenged and frankly I don't feel the same kind of embarrassment I feel in a normal classroom when I don't understand the material or want to ask a question. The instructor was extremely knowledgeable and enthusiastic about the subject which made it all the more motivating to learn. Props to AoPS for such excellent classes!