It is good to be able to do both, slow and fast. I have seen it with a number of shooters that do fine as long as the whole shot process is one smooth continuous motion, but then things breakdown when that accustomed rhythm is broken down. when I flinch, it is usually when I am planning on changing that rhythm up in process. I had for a period that I was shooting about the speed that Hill did when he was shooting coins out of the air, it seemed that every time I would go down in draw weight that I had to consciously tell my self not to rush things for a time. What foiled my accuracy was an accelerating draw speed. The shot should be smooth, there is no law that says what is too fast for one is not okay for another.Hill advocated shooting quickly at game, providing it was not a crazy rushed event. All other parts of what makes good form still applies, just in a continuous, unbroken and perhaps quicker time frame.