I think that's a very good question. I was one of the optimists you mention. It was my opinion at the time that the administration was downplaying (even denying) the impact of U.S. control of Iraqi oil for political purposes. It made sense: the press and the Left were claiming (just as in '91), that Bush was going to war "for oil", and by golly only a satanist would do that.
I have always been of the mind that oil is one of the few things actually worth going to war over. Right now, the fate of billions of barrels of crude should be at our disposal. But we caught a bit of the integrities, and the line is now (as it was) that the Iraqi oil belongs to the Iraqi people. Could be one of the greatest strategic blunders in the history of warfare; but it makes us look nice.
So, there will be no "cheap" oil, as we had hoped pre-invasion. But, at the least, I think you can count on relative stability in the oil markets, because there is a certain amount of fear that we have instilled in the producers.