Is intrapersonal comparison possible? Personal boundaries don't matter for hedonistic utilitarianism, they only matter insofar as you may have spatio-temporally connected clusters of hedons (lives). The difficulties in comparison seem to be of an empirical nature, not a fundamental one (unlike the problems with preference-utilitarianism). If we had a good enough theory of consciousness, we could quantitatively describe the possible states of consciousness and their hedonic tones. Or not?

One common argument against hedonistic utiltiarianism is that there are "different kinds of pleasures", and that they are "incommensurable". But if that we're the case, it would be irrational to accept a trade-off of the lowest pleasure of one sort for the highest pleasure of another sort, and no one would actually claim that. So even if pleasures "differ in kind", there'd be an empirical trade-off value based on how pleasant the hedonic states actually are.