Already, Iran has violated their commitments by refusing an inspecton of an underground site at Natanz:
The officials, who spoke on condition of anonymity because of the confidentiality of the information, told The Associated Press that Iran's unprecedented refusal to allow access to the facility at Natanz could seriously hamper international efforts to ensure that Tehran is not trying to make nuclear weapons.
If Iran was going to make a positive response, there'd be no reason to say no to an inspection right now. Indeed, if Iran was thinking of an ambiguous response to stretch out talks to buy time, I'd think they'd avoid an open refusal.
Oh, and as an aside, I wasn't aware that the international efforts in regard to Iran were an attempt to stop Iran from making nuclear weapons. That these international types think that this is what they are doing is fairly scary.
But anyway, instead of saying yes or wait a couple days because we are in the middle of spring cleaning and the place is a mess, Iran flatly says no. Do they think they need to buy no more time?