One other big advantage of DC is that at numerous restaurants (located mainly in metropolitan areas), you can get 20% off the bill automatically. I believe the restaurants are listed off the website, (in us,
www.dinersclubus.com) along with more info about diners (like primary auto insurance coverage).
Diners also has some great promos, like the British Airways one going on right now--1:1 exchange instead of the 2:1. So, those 24,000 points for the bonus, after one year, can be 24,000 miles. With the first year bonus and a renewal bonus for the second year of 10,000 points plus some charges, I was able to exchange 40,000 points after only 16 months with the card--enough for a BA roundtrip to Europe, off peak.
Plus they have lots of airport lounges, although only a few are in the US.
For anyone needing a DC referral, I'd be happy to part with four AA 500 mile Greenpoints certificates. Let me know.