Dutch, the basis is the controlled testing done in a laboratory environment. The difficulty with any data based on how many terrorists you catch is you do not know how many have tried to get through. My experience is that no single technology has proven to be the panacea. Millimetric wave is good and far better than metal detection.
There are systems that do not show an image at all unless the system detects 'foreign objects' and many countries have protections in place against abuses. The interesting thing is what if a passenger refuses? does this make them a suspect?
In the UK there is no power of forced search for airport security so a passenger can refused to be searched. However, it is a condition of entry so the airport will stop you flying but will that refusal make you a target of police suspicion?
I understand that feedback from trials carried out at airports was generally well received and no big issues from the frequent fliers but i suspect questions will keep cropping up on this one. i would be interested to know how it has been received publicly in Australia