Hoepfully we're not just torturing our audience at this point.
Andrew notes, correctly, that torture can be used to elicit false confessions. The Soviets were of course masters of this technique, with those subjected so pliable they would repeat the false confession in open court at show trials. In the U.S., courts observe strict guidelines regarding how police interrogate and whether such confessions are admissible, because a coerced confession is likely to be false. Yes, you can make someone say whatever you want with coercion.
But the fight against terrorism isn't a court of law, and the intent in interrogation of a terrorist generally isn't a court-admissible confession, or to make someone say whatever you want. The goal, rather, is actionable, verifiable intelligence that can save lives. And at that, coercive techniques excel (yes, including torture, although we do not torture and I don't think we should).
As for waterboarding's risks, yes, it is somewhat dangerous. We accept certain levels of risk in order to offset other risks. For instance, tens of thousands of people die from prescription drugs and surgery. Why do we continue to take drugs and undergo surgery? Because overall, those things save lives.
And Andrew's point about picking up the wrong guy, or one suspected only of trivial knowledge, is a serious one. Coercive techniques cannot be used lightly, and every case should be rigorously examined to determine whether there is a serious threat of people dying without the information being sought. If overly aggressive interrogators do subject someone innocent to a couple minutes of serious discomfort on false intel, there should be consequences, and recompense.
But taking coercive techniques off the table entirely just doesn't make sense. Because maybe we have the right guy.
Maybe it's September 10th, 2001, and you have an uncooperative suspect whom, according to reliable intel, knows the names of some radical Islamists planning one-way flights the next day.
Perhaps some people can say "Too bad for those 3000 people and their families, I don't think anyone should be subjected to a couple minutes of discomfort to save a few thousand lives." I can't.
I think Asimov put it best: Never let your sense of morals prevent you from doing what is right.