I quibble with only one small part of Gladwell's piece. He puts too much emphasis on the fact that David wins with effort over Goliath's ability. This is true of the examples he provides in his story, but the real message is that, as Gladwell says, "when the world has to play on Goliath's terms, Goliath wins." Recognizing what your strengths are and using them to attack an opponent's weakness, especially a weakness that he exposes because of simple convetion, is the essence of the story. If your strength happens to be effort, so be it.
Think about this story the next time you hear someone complaining about breaking up a no-hitter with a bunt, or about not "playing the game the right way," or about how big sluggers "clog up the bases." It's just Goliath complaing that David won't play by his rules.