Iran would never have to actually use the bomb. the possibility and the threat that they would make the bomb available to Hezbollah or hamas would gradually erode any deterrence that Israel might have. Those in Israel who could afford to do so would be leaving in their tens or even hundreds of thousands. It would be the beginning of the end. Quite frankly, I have no idea whether it would be a good idea or not to try and pre-empt. I and the rest of the uninformed public simply don't have the information necessary to make such a judgement even if they had the capability. But I do trust the Israeli cabinet to make the best decision. Keep in mind that the security echelon was also against taking out the Iraqi nuclear capability and the Syrian one. I accept that Iran is a completely different kind of proposal but the track record of the security services is not that impressive in this regard.
Week of floods kills 22 in Vietnam (DPA)
from the article: Can Israel live with the Iranian bomb?