In addition to my subjective impression that they take longer to scan - and so are contributing to slower security lines - I hate that they have these external blue and red lights. Objectively, those lights play no role in the scanning and cannot enhance security. This is not a consumer item, so it doesn't need to look cool.
Or does it? Did the salesmen at the manufacturer suggest to the designers that cool lights would impress the TSA bigwigs with the machines' futuristic and make them more likely to choose them over competitor' perhaps cheaper but less exciting looking product?