In my opinion, Dima hits the nail on the head when he categorizes any method as restrictive. Yes, certain generalities, even helpful ones, can be gleaned through perusing them and I'd admit to using some such insights in my own playing. In the end, though, I believe that playing the piano is far too involved and complicated an activity to be neatly analyzed. Science has its limitations: imagine an apparatus that successfully tracked very physical component of virtuoso playing along with the precise muscular force expended per fraction of time. Assuming such a device was possible and generated an accurate graph reflecting every element, how would you assimilate the conclusions? Observation combined with intuition and even osmosis (in the sense that we can learn by watching accomplished performers), using as relaxed a mechanism as practical that's enlivened by musical comprehension seems to me to be the way to go.