There are many ways to work kata and each will give you a differant take. Be it change the speed, or timming or do it backwards. All of which are good. I don't really agree that one should go as fast as they can because certin combos take time but I do see the importance of developing speed. I do agree that most people do not do kata the correct way. This usually has less to do with the speed but the application and practice of them.