I would add, also, that Saddam's past actions have not been notable for their rationality.
If one were to judge from his ill-advised wars with Iran and Kuwait, not to mention his internal use of WMDs, one cannot very easily dismiss the possibility of Saddam impulsively popping off a nuke (at Israel, most likely), in the expectation that the Islamic world would rally behind him.
I don't think that we could get lucky enough for Isreal to get rid of the Iraq problem for us. I really believe that if one ounce of nerve gas or one case of smallpox (not to even mention a nuke) pops up in Israel, and Iraq will cease to exist within minutes. If we're lucky, Sharon will give us a "heads-up" to get any people we have out of there and I would expect that notice to come AFTER the missiles have left the silo.