Cannot use this fine control on high speeds. The visible screen don't jump fast enough from one event to another, the mouse clicks and button pushes take some time to execute the given commands. So, you cannot make enough movements in a unit of time. The problem is exactly cause the keyboard and mouse reaction at given commands are much slower than I think and I move my hands and fingers to use mouse and hotkeys. In campaign, the AI superiority in start resources, in gathering rate, in number and kind of units, the almost continuous massive attack waves, the countdowns, execute anyway a constant time pressure over the player, so anyway you must think and react fast, to be competitive. Otherwise, not fast thinking and reaction are the point, so long you can save and reload the game. The problem is cause that speeds take from you the real time control above your own army, control which DEFINE a RTS. And that make the game more annoying than harder. In multiplayer, that lead at a drastic limitation of usable tactics and strategies. Even the greatest players are forced to use always the same limited ways to play, based on early rushes, so, the existence of most of the units above MMM, helions and eventualy vikings (or the corespondent for other race) become useless in the game. So, at high speeds, in campaign or multiplayer the player cannot use the most of the game resources.
And I don't understand why so many want to limit the liberty of others to make their choices, to play at any speed at they want, so long nobody force themselves to play slower! And if Bliazzard don't want to modify this lack of speed control, I definitely not will buy the next chapter!