I have used it for years and love it.
If you are not well, flu or other lurgi it is a blessing to have a delivery of shopping and my mobility is so poor that I have deliveries once a month or so, of the stuff that is heavy to lug about, washing powder in big boxes of bulky things like toilet rolls, boring stuff like bottles of ketchup and tea bags, flour, sugar, dog food. For the small cost of delivery I save myself a lot of pain and they do seem to turn up however bad the weather is too.
Christmas orders can be a bit haphazard but I get things a couple of weeks before, and then just order any meat I need from lovely local butcher.
Amazon are going to be doing same day deliveries, so I expect others will follow with that as well.
Having the shopping brought into the kitchen for me means 2 lots of lugging the stuff about saved every shop, once into car, once out, when pain is your master it really is a boon.
I specify live alone and long use by dates, and they are happy to take stuff back if you don't l ike the look of it on the day.
It is a fabulous service for older or disabled people or even just busy people. You can have a delivery booked for when you get home from holiday or hospital.
I don't tip the driver, not sure they are allowed to accept it.