Unless Israel attacks Iran, i do not see Iranians using Nukes.
Even if they were pushed in a situation to Nuke Israel, the presence of Palestinians will still be a major factor checking such a decision and complicating the matter for Iran.
Iran's nukes will serve as a deterrant but they will not be trigger happy, they have a lot to lose in case of a Nuclear war.
I am just not sure how rational the differant religious groups in Iran are that are in Power and Iran has a long history of supporting terrorist,,Then there is the Army of the Guardians of the Islamic Revolution, do you really want to take the chance of what will happen if some extreamist happen to decide to attack Israel ,if just one bomb gets in the hands of the wrong people and are used on Israel all hell breaks loose...no country is going to be understanding if a nuclear bomb goes off in it tomorrow...
Remember the deterrance of Israels Samsons Doctrine is they attack every body if they are on the point of being destroyed....not just Iran..