So what you get is a very fluid experience where the units react when you tell them to.
While this is good in concept, I fear it may upset the balancing of some of the stronger units. In the videos I've seen, the Mammoth tanks turn instantly, as do their turrets. Since the Mammoth tank is supposed to be a slow unit with lots of armor and firepower, having a slow turning speed for both the unit and its turret would be more balanced, as it would allow for quicker, less powerful units to outmaneuver it. You could do this against Overlord tanks in Generals and it worked well (if you had good micro), promoting unit mixing to balance out the weaknesses of any given unit.
If every unit in C&C3 can turn and aim instantly, there will inevitably be balance issues.