Wegmans recently introduced carts with built-in scanners and scales to allow you to scan as you shop—I really like them overall, and use them every time I go there (which is only once every few months; it's 45 minutes away), even though I often need to get a second, regular cart to offload some of my bags to partway through shopping.

The one problem I've had with them is that they have a tendency to get confused if you try to scan more than one of the same thing in a row, and occasionally I'll have to go through quite a bit of trouble to make sure that I do pay for the 3rd item, and not just the first two...