The WaPo's fact-checker rules largely in favor of McCain.

We do not have enough information to make a definitive judgment. But it appears that Mukasey is straining to make a connection between the killing of bin Laden and the harsh interrogation techniques [sic] that appears, at best, tangential. Otherwise, he would not have had to resort to verbal sleight of hand to make his case. McCain, by contrast, appears to clearly connect the dots from the courier to bin Laden, citing information derived from conventional techniques. At the same time, while the enhanced techniques [sic] may not have provided the Rosetta stone to bin Laden’s whereabouts, Mukasey may be right when he asserts that valuable leads in the broader war against al-Qaeda were derived through these techniques.

Mukasey has now conceded that the name of OBL's courier did not initially come from torture, just that KSM's lies about the courier alerted the CIA to the significance of the name.

What I find interesting is Thiessen's assertion about the nature of the torture program. He claims it was not torture because the torture was not designed to elicit direct answers; it was designed to break the will of prisoners to lie by destroying their psyches and souls through physical and psychological terror. So they'd be tortured unti they broke down as human beings; then, after they had recovered from the repeated drowning, freezing, beating etc., they would become "compliant". Here's Thiessen's explanation:

McCain was briefed in detail more than once on enhanced interrogation [sic], so he knows full well that enhanced techniques [sic] were not used to gain intelligence from detainees — they were used to compel their cooperation. While applying enhanced techniques [sic], interrogators would ask detainees questions to which the interrogators already knew the answers, so they could judge when the detainees had made the decision to begin cooperating. Once they did so, the techniques stopped and the detainees moved into noncoercive debriefing.

One supposes this is designed to avoid the obvious point that prisoners tortured to give information often tell lies to get the torture to stop. But what Thiessen articulates is, in many ways, more disturbing.