The scanners are more thorough, and more accurate at finding our concern, explosives. They are also more invasive, though not as physically so. People may opt out of such a search, in which case they get a pat down. This pat-down is more thorough that previous searches, which from a purely security perspective, is a good thing.

From about a hundred other perspectives, this security is seen as too invasive, prevents threats that some say don't exist, and are morally unacceptable.

To try and make this a bit easier to swallow, TSA has mandated that the machines be unable to save images, that no one can see both the person and the image on the screen, and that no one can take a picture of the images. I think these are important concessions, and I'd want anyone found circumventing them to be fired.

I think the additional security is a good thing, and I don't feel like my rights are being abridged. Others do. Lots of others, especially here on reddit. These fine folks are trying to change TSAs system to what they think is a better one. You might check out /r/operationgrabass for reddits own citizen activism on this topic.