Been using the Amex cashback card for about 3yrs now. The number of places that use it have sharply risen in my experience here in London. Hell even my newsagents here accepts it. The only place that doesn't, is my Barbers and the local Fish & Chippers but these two only accept cash anyway.
My spending is low these days so the cashback is rather minimal and the rewards/offers have always been pretty crap - places that are in central London for stupid money like hotels and Selfridges, or dining in places I've never heard of. I'd prefer more techy shopping places instead of hotels, travel and ridiculously priced dining experiences for money off.