Some American Express cards are still charge cards, while many are credit cards (and some are charge cards with the ability to "pay over time"):

http://www201.americanexpress.com/ap.../b/12&us_nu=dd

If one pays the bills in full each month when they come in, these effectively are the same. If one doesn't pay in full, that's when the differences in fees and interest rate calculations start to come into play . . .