Michael Ledeen argues money was exchanged:
So to all those who are looking for subtle reasons for the Saberi release, take it from someone who has been there. Iran collected its ransom. The mullahs aren't subtle, they're mafiosi. We probably won't know for a while what they got, who delivered it, and who worked the deal. But anyone familiar with the workings of the Islamic Republic has to assume that there was a payoff.
I don't know, but I do worry that this kind of certainty and broad generalization about "the mullahs" sound very much like the rhetoric that talked us all (well, not all) into believing in Saddam's WMDs. Just because some of them are assholes and kleptocrats doesn't mean they could not also be adjusting to the Obama era a little. If only for self-preservation.