I played a lot of beta SC2 games (as random) with the grid setup and managed. Since then I've started watching Day[9] and some other commentators who seem to refer often to the default hotkeys in their recommendations for, eg., keeping drones building at all times.
My question is: to what extent are hotkeys mere preference? If we took a random sampling of competitive players, would roughly 50% be using the grid layout, or would it skew for some relevant game-play reason?