This is why Kay thinks we should continue this effort:

Why should we take the time and run the risk to ensure that our conclusions reflect the truth to the maximum extent that is possible given the conditions in post-conflict Iraq? For those of us that are carrying out this search, there are two reasons that drive us to want to complete this effort.

First, whatever we find will probably differ from pre-war intelligence. Empirical reality on the ground is, and has always been, different from intelligence judgments that must be made under serious constraints of time, distance and information. It is, however, only by understanding precisely what those difference are that the quality of future intelligence and investment decisions concerning future intelligence systems can be improved. Proliferation of weapons of mass destruction is such a continuing threat to global society that learning those lessons has a high imperative.

Second, we have found people, technical information and illicit procurement networks that if allowed to flow to other countries and regions could accelerate global proliferation. Even in the area of actual weapons there is no doubt that Iraq had at one time chemical and biological weapons. Even if there were only a remote possibility that these pre-1991 weapons still exist, we have an obligation to American troops who are now there and the Iraqi population to ensure that none of these remain to be used against them in the ongoing insurgency activity.

I had not even thought of the first reason, but I think it's the most important of the two. The gap between what intelligence thought was there and what was actually there needs to be analyzed in depth, or we won't learn what it takes to get things nailed down more accurately next time. This is true even if the intelligence flaws were due to deliberate deception from Iraq, since other nations can use the same tricks.