I have had an Asda card for about a year now, unfortunately the Asda near us doesn't have a filling station, the nearest is about 7 miles away so we only take advantage of the cheap fuel if we are out that way anyway.
The rewards are good on the card though, you earn the same amount of points for shopping anywhere as you do for shopping in Asda though which is a tad odd, handing over my Asda card in Tesco's feels quite funny
Have earnt just over £20 worth of Asda vouchers so far this year just using my card for general day to day stuff, they get sent out in December before Christmas.