...from NYC to Miami and back for a business trip.
I opted out of the full body scanner in Miami but at LaGuardia I was in a security line that only used a traditional metal detector so I didn't have to face this issue.
The TSA agents were very polite, both the gentleman I told I wanted to opt out (he replied, "absolutely, that is your right") and the female agent who did the physcial pat down. She was obviously using a prepared dialog that she was trained on and she did so very politely.
Many people and news reports say that these new machines are perfectly safe because they emit very low levels of radiation, but since it took me 6 years of TTC with medical intervention to get this far along I don't want to leave anything to chance.