Juan Cole makes the case for engagement:
It is not true, as Robert Kagan once alleged to me on the radio, that if something is in Iran's interest, it will do it anyway, so that talks are useless. It is often the case that countries, like individuals, cut off their noses to spite their faces. Effective diplomacy can often lead a country to see the advantages of cooperation on some issues, so that its leaders stop sulking and actually turn to accomplishing something.
I'm still a skeptic, but see few other good options right now, apart from trying to stall the nukes with sanctions, help fund the domestic opposition, and hope that Iraq's centrifugal explosion may soon give the mullahs in Tehran a headache. Cernig is a skeptic too, if for different reasons:
Talking is almost always vastly preferable to bombing. However, I've a nasty feeling that these talks will, eventually, go nowhere - and will then be held up as evidence of Iran's lack of amenablility to diplomacy by pro-war Bush administration members and their enablers.