However, here in the Wild West we don't have those Amazon shops, and there is one huge difference between the M&S experience and the scanners in conventional supermarkets. Go round Waitrose or Asda, say, with a self-scanner and you end up with a trolley load which you take to a till and pay for under the watchful eye of staff. But the M&S app lets you walk around the shop (food section only) scanning stuff and sticking it straight into your shopping bag. At the end you pay on the app, then walk out of the shop, never going near a till.
This is especially useful in our local Marks and Sparks as they only have three self-service tills, crammed into a very small space. But the benefit is not just time-saving on queuing for the till - the biggest boost is the aspect in which it's closer to the Amazon experience than conventional supermarket scanners. There is is simply a wonderful frisson of naughtiness that you get from taking something off the shelf, giving it a quick scan, then dropping it straight into your shopping bag. It really is rather exciting (I probably should get out more).
Clearly this kind of thing has the potential for misuse: after you've paid on the app, you get a screen up with a list of what you've bought which you are encouraged to keep ready, just in case a staff member stops you on the way out. Even this adds to the experience - the possibility of someone pouncing on you and being able to say 'Sorry, it's legit,' with a big grin.
Where I live, we have three food shops in walking distance - a massive Asda supermarket, a smallish Lidl and Marks and Spencer. I'd never do a major food shop at M&S - it's all about picking up a couple of things they do especially well - so this is ideal for my kind of shopping. Anyone need anything? I want another go...