Scouring a couple of forums real quick on transgenderism and post-op communities, it seems as if they are more reluctant to bring up any dissatisfaction felt out of fear of being ridiculed even more.
Renee Richards and Dani Berry are two of the most famous, outspoken people who had undergone resassignment surgery only to later learn that it was for the wrong reasons. While pre-op care has significantly changed in many communities throughout the free world, there is still not enough evidence to suggest that transitioning is medically beneficial. Those who were in bad situations, emotional/mental places, or bad personal relationships will often remain in those situations after surgery without proper post-op therapy. Whatever, proper post-op therapy actually is for a person with GID is up in the air.
I cannot imagine what one most go through when they wake up post-op and realize, the parts are different but the brain is still the same. The parts are just now, non-orgasmic in most cases.
Renee Richards thought she had it all figured out and was well on her way to being the person she had dreamed of being. In her autobiography she states that she was just a sex obsessed transvestite and did not suffer from GID.
So, essentially the point is there is a very real possibility that the therapy approach taken in the medical community is entirely misguided and GID can sometimes mirror the issues of another disorder. Those presumed to have GID are often too afraid to tell their therapists every minute detail that would distinguish the difference between GID and say, disassociative disorder.
Additionally, I believe there are far more MTF in the world that do not want bottom surgery and are happy to leave things as they are. Regret comes in many forms and it doesn't always revolve around the actual procedure. But, is instead a result of intolerance, ignorance and the let down that they still didn't feel like a natural woman or a natural man as they had so desired. This leads to increased depression, isolation and in some cases - suicide.