I am using PF for only a month. And I think this is the best website i've ever visited. When I first came here, I was quite grumpy about the fact that I have to show equations, my work. However, I think it is a very good policy right now. Some of the students depend entirely on internet to solve their homework. They just type their questions in AnswersYahoo or something like that. As they keep doing that, their ability to study degrades. And they will feel not much good to see their grades in exams, for they have never used their own head to solve homework. I will recommend this site to everyone in my math and phys class. The site require us the show our work so that lazy students don't just pickup answers form hard working smart people and leave. This site enables students to think about problem, analyze it, and solve the problem by themselves. There are lots of good people here who like to discuss about science, try to help people troubling from science problem, and suggest them the methods to help them out, give advices. i started to love it here. Thank you to all of the good people who replied to my questions.