Waterboarding really isn't half of the story. A really interesting BBC documentary reveals information about undisclosed detention centers in Iraq run by Iraqi's under US direction. Rumsfeld brought in an American that had previously been involved in the El Salvadoran death squads, used to murder civilians and prevent democracy there back in the 80's. A man named James Steele. He worked hand in glove with Patreaus helping to run gruesome torture chambers. Men would just be picked up, tortured, and finally just murdered and their bodies dumped in the streets.
Thanks to Wikileaks and Bradley Manning we learned that the US military directed US personnel to not report torture that they witnessed (see #9 here), which itself is an international crime. While Steele today lives in Texas and is paid to do security consulting, Bradley Manning sits in prison for trying to do what the law required; make people aware of the crimes that were happening.
Patreaus finally did get in some trouble. Not for torture. He had an affair, and subsequently resigned. That for some reason drew the interest of the US media. But not torture. Recall that the existence of torture chambers was one of the justifications offered for overthrowing Saddam.