I realize I'm really late to the party on this Gates Iran memo story but, to be honest, I find it mostly overblown and par for the course of internal administration dialogue (Richard Haass, keep in mind, pieced together thoughtful memos of dissent back in 2002 and 2003, yet still supported the eventual invasion of Iraq).
Marc Ambinder, drawing a parallel to the 2005 NSA disclosures, writes:
'Whoever leaked this memo to the Times has to bear the responsibility of knowing that they could very well have fortified Iran's intention to resist international pressure, that it could very well have complicated the careful cultivation of China and Russia on sanctions, that it could steel Israel's spine in ways that would be perhaps deleterious for the region.'
My reaction: Eh. I think this is a classic case of beltway over-thinking. Think about it from the Iranian regime's perspective: you're covered on two fronts by tens of thousands of U.S. (and other Western) forces; Washington is arming and rearming your regional foes; it's rather obvious that either Israel, or the United States or BOTH are engaging in some sort of covert sabotage campaign against your nuclear ambitions, and one of your nuclear officials just defected to the West - a defection obviously facilitated by your enemy, the Saudis.
One memo doesn't change these realities for the Iranian regime, it simply affects the minds and already entrenched opinions of those in Washington.