I just used a U-Scan terminal at the Ralph's. It's a nicely set-up system, but some parts of it are weird. After you scan something, you have to put it in the bag... the machine is waiting for the weight to increase before you can scan something else. It has a certain inexorably robotic logic about it.
Similarly, when you pay by cash, it wants you to stick coins in first. That's because (I assume) it's programmed to give change as soon as the money you've stuck in is greater than the total. So if the total were $19.01, and you stick a $20 in, it'll spit out the .99 before you can put the penny in. You'd think it'd be easy to add a button that says "Ok, now I've stuck in all the money I want to. Gimme my change." But that would require an extra button push. And it wouldn't protect the machine from situations where Mr. Magoo keeps feeding in $20's ad infinitum. Again, I can appreciate the precise logic behind this design element. But it's still alien.
Lastly, as a totally hypothetical example, if you run a bottle of tequila past the scanner, you need the inattentive drone manning the station to check your ID.
I was a bit slow this time around, but I feel ready to U-Scan again. We're getting closer to my perfect world, where I won't have to interact with anyone at all, unless I want to. The best part was that the machine didn't notice that I had three bottles of scotch under my shirt.