Since our intelligence estimates are so often wrong, the neocons might still be right about Iran’s nukes. And, if not, it’s only because the neocons were right on Iraq!
I think it's possible that U.S. activity in Iraq may have had some effect on the Iranian decision. First, the destruction of Hussein's regime removed the greatest threat to Iranian security, and ensured that Iran would have a greater influence over Gulf affairs whether or not it produced a nuclear weapon.
For my part, the news from the NIE comes, obviously, as a relief, although I think it's fair to take all judgments from the NIE with a degree of salt. I don't think it means abandoning diplomatic and economic pressure on Tehran; but I do think it removes all likelihood of this administration launching a new war in the next year. This will be the next president's problem, and we have to ask: who is best capable of delivering a strategy of careful threats and inducements?