It, for many people, works differently. If you look at people talking about their experiences, those with ADD consistently describe different effects than NT people. It's still good, but it has more of an effect on energy than focus, though the two are well correlated. It might be an overshoot/undershoot thing, it might be that different effects are salient, but I can assure you that if Adderall could do as much for a healthy person as it does for me, we'd be living in utopia.