I am a paraplegic man, due to an automobile accident 25 years ago. Thus, I have tried to stay somewhat informed, on any medicine that could have an influence, on my disability. Therefore, needless to say, I have some personal insight on this issue.
The closer we get to being able to alter and modify the human body, in ways previously deemed "unethical", the closer we humans get to making God and Nature...no longer ethical.
There are steps being taken today, that just a few years ago were considered unethical, if not irresponsible. Yet, with time and sensitivity conditioning, belief systems change. Now, what is accepted as "progressive" or "forward thinking", was once thought of as "un-natural" or even "playing God".
I do not claim to know why we continue to change what is ethical or acceptable. Although it seems logical that ethics change slightly in tow of medicine and technology. IF, this is true, then I say that Genome Mapping is possibly too far ahead of ethics on the curve and should be put on hold, until the understanding, of what it means to humanity at ALL levels, has been brought forward also.
Of course there is no turning back, nor should we, but there is still the ability to control where, and how quickly, we go forward. Once we have gone too far, too fast, then it cannot be undone. The fictional story of Frankenstein still has very non-fictional messages for today's Medical World.
So, what will be the biggest benefit for human beings from mapping the human genome? I do not know. I just hope we spend enough time figuring it out, before we find out.