The economist's utility function is not the same as the ethicist's utility function. The goal of the economist is to describe and predict human behavior, so naturally, the economist's utility function is ill-suited for normative conclusions.

The ethicist's utility function, on the other hand, summarizes what you actually want, should you have the opportunity to sit down and really think about all of the possibilities. Utility in the ethicist's sense and happiness are not the same thing. Happiness is an emotion, a feeling. Utility (in the ethicist's sense) represents what you want, whether or not it is going to make you happy.

If this isn't entirely clear, consider that both happiness and the economist's utility function (they aren't the same thing either, mind you!) summarize a specific set of adaptations which would lead the actor to maximize his or her genetic fitness in some ancestral environment. The ethicist's utility function summarizes all of your values. Sometimes - many times - these values and adaptations come into conflict. For example, one adaptation for men is to treat a step child worse than a biological child, including up to (if getting caught is unlikely) murder. This will not be in the ethicist's utility function.

side note: Nozick's experience machine is no problem for the ethicist's utility function. Do you see why?

p.s.: you might want to reformat your link