[jharger]

That's kind of the key, right? If you're buying one or two items, the self-checkout is great! If you're buying a week or two worth of supplies, it's terrible.

Here in the US, at least at the stores I shop at, each item requires that you scan it, wait for the machine to tell you to place the item in the bagging area, wait for it to register the weight, then you're allowed to move to the next item. If you accidentally wait too long, and the attendant just clears the wait state (which they do all to frequently just to get things to move along), then it won't let you put the item in the area, and instead you have to call the attendant over to clear the "unexpected item" state, which just makes things take so much longer.

Then there's the times where some older person tries it out, gets really confused, and the attendant is spending all of their time with them, and everyone else gets held up by the quirks of the system.

[justincormack]

It depends on the store design, Waitrose in the UK doesn't bother with the weighing thing, and you can scan as you go around the shop and just pay at the end. It is way more convenient.

[jharger]

One supermarket I went to tried that... but the user experience is so awful that no one wants to do it, so the scanners just sit at the entrance, lonely and unused.