effortless power, not powerful effort
I completely agree with what Andru has said.
Before rebuilding my swing, I would try to generate clubhead speed with my arms and just take a massive rip at it. The usual result was a monster slice with not alot of distance.
Since rebuilding my swing and being taught turn, coil and weight transfer, my swing feels like 30% of the effort of my old swing and the ball carrys farther and straighter than ever.
Although most would argue against following strict fundamentals, I have to say that by following them to rebuild my swing has increased my clubhead speed by 15 mph and it's all attributed to technique and form rather than power.