Simple answer - yes. Sunday evening in the middle of Northern France, about an hour and a half from Le Mans. Pulled in to an unmanned petrol station, registered card, filled up, rode away.
One point to note is that the card is "virtually" charged for €130 before you start filling (similar to pay at the pump machines here). If you don't have a credit balance of €130 it won't work.
I used my Caxton card in the Carrefour petrol station in Laon in May and then found that I could not draw enough cash out the cash machine and had to use my debit card for it. It still worked at the other petrol stations though.