I have a Costco American Express card that I rarely use because I hardly go to Costco. I used to have the Air-miles card and switched out that because after I did math I realized that on average I was earning 0.68% from my purchases, that to me is a rip off. I now use my MBNA Platinum Plus Smart Cash card and get 1% back from everything I purchase, and 3% from groceries and gas.
The only reason why I'm keeping the American Express card around is because they have the best customer service. It too bad they have the worst reward credit cards.