As I have argued a number of times in a number of different contexts, none of the Democratic candidates currently in the race have any executive experience save for long shots Gov. Bill Richardson (the current Governor of New Mexico) and Dennis Kucinich (as mayor of Cleveland). Byron York also talks about executive experience and dismantles the case the Hillary Clinton seems to be making, that as First Lady, she has executive experience.
Leaving aside the issue that she attained her "executive experience" and position by merely being married to a man who was elected President, her track record is not particularly stellar. Add to that the fact that no one--except maybe her own direct staff--ever had to follow any of her orders. She lacked not only a definable position, but also anything resembling authority.
I think that the reason why none of this has come up is that no one currently in the race, aside from Richardson, has any chops to question her experience. Obama less than one term in office, Edwards only had one term and the remaining candidates don't have much of a shot at this time. But, assuming she wins the nomination, Clinton's "executive experience" will be severly questioned if the GOP nominates Giuliani or Romney and if Thompson is chosen, he has as much experience as Clinton in the Senate.