Originally Posted by JerryFF
I would suggest that you consider Diners Club. I know many people don't like it because of the very high annual fee and the charges they impose to transfer points to airline miles (though not hotels). However, there are two shortcomings with the SPG AMEX (which I agree is an excellent card) 1) there are still many merchants who do not accept AMEX, (Diners Club is now treated as a Mastercard and is universally accepted) and 2) Diners Club allows transfer to a few airlines and many hotel programs that SPG AMEX does not.
It can be well worth having more than one credit card, though of course for some people it may be risky (spending-wise, that is).
I find that more and more merchants do accept Amex; for example, some time ago, Safeway began accepting it.