And yet, from the link:
Defenders of waterboarding, which was declared to be torture by the Obama administration, claimed it led to concrete results. They said that its use on Abu Zubaydah led to Khalid Sheikh Mohammed, the mastermind of the 9/11 attacks, and that the latter’s interrogation using waterboarding led to the location and killing of Osama bin Laden. Former vice-president Dick Cheney claimed that the techniques produced “phenomenal” results.
My own take on it is that the waterboarding had a psychological effect on the detainees to the extent that once confronted with newly gathered evidence they were reminded of what may occur if they did not confirm the intelligence, a sort of carrot and stick.
I know it's Hollywood but the film Zero Dark Thirty covered the subject and it's widely accepted that Bigelow(director) got it pretty accurate, so I'd go with that.