We have one of these. It is great to get a few bob off the bill every time it comes in. Shown at the end of the bill as "cashback" and normally in the region of 12~14 € (on a spend of 2,500 € per month approx.). We tend to buy everything through the credit card, including petrol, groceries, insurance etc, and of course pay it off fully every month).
This amounts to roughly 125€ a year.