There is an element missing from the question posed here. That is, it addresses the question only from perspective of the effects of toppling Saddam.

Let's ask this question: Where would we stand if Saddam were still in power. (1) Would we still be trying to keep him in his box and, what would the cost of that be? (2) If we tired of the cost of keeping him contained, would he give up his designs to control Arab oil? Would he stop making war on his neighbors. Would he stop exterminating anyone who disagrees with him? (3) With Iran building nuclear weapons, would dear ole Saddam sit quietly by and do nothing, or would he engage in an arms race with the ayatollahs?

I would submit that Saddam would likely be an even bigger problem today than he was 7 years ago. The military cost of keeping him down probably would have been less, but it takes little imagination as to what the political cost would now be on the price of oil with both Iraq and Iran going at each other yet again.