I agree with all of the above and would add that I like a place to be clean, bright and welcoming and I absolutely hate waiting to pay, or having to search for a till to pay at. I will always remember a store that goes out of its way to help, e.g. finding a product for me.
I remember being deeply impressed by a major store in the states which gives people with disabilities a pleasant, smiling personal shopper to go around with them and collect their goods from the shelves and help them pack and get goods into their cars. That kind of service not only helps the disabled shopper but leaves every shopper with the impression that the store really values them. A real win/win for all concerned service.