My biggest problem with this is that from what I can tell, the only way to know how much you're going to be automatically charged (as well as what items the tech thinks you're purchasing), is to go to a kiosk in the store and get a receipt. Which seems to completely defeat the convenience of just walking out in the first place. I wouldn't feel comfortable just walking out without knowing how much I'm going to be char…
With Prime Now, you get your groceries delivered and pay for them in advance. Once in a while, you don't get an item, get the wrong item, a rotten piece of fruit, or an expired bottle of milk. When this happens, you simply go to the app where every item is listed, and follow the quick prompts to get a refund. You can optionally give a reason for asking, but in my experience they don't actually seem to care; in fact, whenever I've left a comment that, for example, one of the ten oranges I ordered was bad, they've always refunded me for _all_ the oranges on my order. I assume this is because the number of refunds is low enough relative to the number of purchases that they can afford to just always refund, keeping the customer happy enough.
If this is how it ends up working, then I'd gladly trade standing in long lines at the store for just walking out and reviewing my purchases later. The tracking part is still a bit creepy, though.