Club shop has always taken them apart from the first week or so when the stadium opened. No costs associated with owning one whatsoever, so long as you pay off your balance every month.
The commission issue is often a misnomer, often their commission rate is the same as, or cheaper than other...
I’ve had one since the Amex opened. Use it all over, including in both Asda and Aldi, there are a few places that don’t accept it, but in the main it serves me just fine. And we get Avios (air miles) with everything I spend, which gives us some decent discounts on flights.