I’ve only had two goes at using them. Both times failed. First time the item was discontiued even though it said they were in stock, over a week later a gentle nudge email and no answer. Then another email to be told sorry that item is discontinued. A few days later another polite email from me asking if I could possibly have my money back then? (as they deduct funds straight away). So I got the money and obviously cancelled the order. Tried again, similar story, item in stock and over a week later just another polite enquire email and then told no we don’t have any of those anymore. So cancelled and got my money back straight away at my request. Guess I was just unlucky.
I’m sure there will be plenty of people who use them without issue.