I often try to predict the value of the items in the shopping cart when waiting in the cashier queue. Most of the time shopping in a supermarket, I can predict the total sum in a range of +/- 2 Euros. My girlfriend? Perhaps in a range of +/- 5 Euros. My mother? She would only be irritated if the sum is at least 10 Euros above what she expected. And that is for 15-25 items and a total sum in the range of 40-60 Euros. But there is no way my mother, my girlfriend or even I would detect small over- or undercharging most of the time.
My local supermarket has some specials which are loyalty card only, so when the item is scanned the full price shows up. I use this to determine when to use the loyalty card for minimum tracking, minimum time, and minimum price (it doesn't have my personal info associated with it, but still connects purchases and it's faster to skip).
This is hugely beneficial to individual shoppers. Lining up is such a PITA. Walk in / walk out would be awesome.
They should just have a rule that kids aren't allowed to come along. I can tell you that rule alone will have a zillion mothers crying out in gratitude.
Children could get a military ID at age 10.
So up until 10 I sat outside the PX waiting for her to finish shopping.
(Getting the ID was great, we could get on the base by ourselves with them. We'd ride our bikes out to the Air Force base and hang out near the runway, watching the F-104's take off. Seeing (and hearing) a squadron of them lift off was incredible. Sadly, I had to surrender the ID at 21.)
There still seem to be many of the issues people brought up a year ago, such as how this depends on the presence of a phone with the appropriate app installed, or what happens with groups of people in which only one person has the app (such as with kids).
More to the point, I can see how this would be better for Amazon, but I'm not sure it's better for most shoppers. Amazon gets to charge people who graze on produce while in the store, and kids who consume snacks in the store, and can presumably produce video evidence when customers throw a fit. But they can also overcharge me for things and how am I supposed to know that? Check the app in the parking lot to make sure I have everything it charged me for? What recourse do I have if not? What if something wasn't charged as marked on the shelf? I've already paid at that point. I've gone through this enough times with stores high-end and low-end to know it's inevitable for Amazon.
The leverage is all Amazon's, and the convenience doesn't offset that for me. I know I'm not alone, but maybe there aren't enough like me to dent their ambitions.