If you have a utility function, I can predict your preferences from it. If I want to know what you'd pick when given the choice between an apple or a banana, I don't have to ask you. I can just consult your utility function and see which ranks higher.
If you're looking for a utility function that reproduces human behavior in all contexts, I'd say the empirical evidence is overwhelming that humans don't have utility functions, bounded or otherwise.
If you're looking for a utility function that merely reproduces human behavior approximately, how good does the approximation have to be in what circumstances? Does the utility function that someone "has" reproduce his behavior when the behavior is mediated by conscious philosophizing, or when it's mediated by his gut? If conscious philosophizing, how...
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.