I wouldn't care if they ran OS/2 or DOS.
But could we please just make them so that they aren't so damned tied to that stupid weighing scale thing on the bagging area.
Honestly, just turn it off. If I wanted to steal something, I just wouldn't put it through the till in the first place, and my receipt would always clearly show what I SHOULD have in my possession and what I shouldn't. And likely you'd want to steal things like microSD cards or something expensive-but-light that wouldn't even register, or you'd scan something and then put something weighing the same on the scale anyway. Nobody ever checks, even if you call someone over.
Stick a camera directly in the machine to watch what I scan/place on there, and then turn off the stupid scale thing that whines at me until I manage to arrange the bags in the exact configuration that it needs to sense "previous weight + 0.5g of envelope" or whatever.
Honestly, it's a brilliant technology, totally hampered by a stupid implementation. And, yes, I have seen stores where they turn it off... Poundland sometimes has them. It works so much better without that nonsense.
Fix that and you could run the thing on hand-coded assembler for all I care.