It shows you naked but not in any great detail but I believe you CAN make out private parts (I saw the tech on BBC News Technology site a while back) but the images "aren't stored" apparently. It had been trialled in Heathrow for a while before El Gov't decided to roll it out.
Apparently the Yanks already have these scanners at certain major airports too.
My view on the Child Scan thing is that - If certain demographics got out of it, then there's no point in it at all.
However I do think that our civil liberties are being eroded away bit by bit. It won't make us safer...if people want to find ways around them, they will, regardless of the security measures.
My issue at the moment is: The scanners look like stand up ones... How do amputee's or disabled people get scanned if they are in wheel chairs?? (However this is off-topic so I'll shush
)