There have been two recent publications from the University Medical Center Groningen in the Netherlands, one looking at muscle contractions and the other blood flow in the brain during female orgasm. One of the findings was that either faking an orgasm, or failing to achieve orgasm produces different effects, and according to the first paper, it is the first time a physical measurement has been shown to have a strong correspondence to subjective reporting. I presume that would be helpful in treating disorders.
I vaguely wonder how typical a sample of the population they had there. It has to be a certain type to volunteer for a study like that.
A more readable report (and very interesting too) from 2005, published by the Wellcome Foundation, gives an account of twin studies (plus some others) which show that there is a strong genetic factor in ability to achieve orgasm. It also adds that the Dutch researchers had difficulty studying male orgasms because the imaging techniques they used required a response lasting two minutes.