Diners is my card of choice and last year I earned some 20000 miles by just buying things that I had to buy anyway. But I've found it's not so widely accepted in the USA. In Scandinavia it's very widely accepted and you get 30% more points over American Express. From time to time, I've found the lounges good as well. It's perhaps less of a benefit now that the big airline alliances are offering so many reciprocal lounge benefits - at least for their elite members.