FYI. AMEX has a promotion through the end of June -- spend $200 on your enrolled card and get a $50 credit on your statement. I bought some stuff on Friday when the semi-annual sale started. Moments later, I received an e-mail from AMEX informing me that my purchase triggered the credit.
Details from Fat Wallet here: http://www.fatwallet.com/forums/hot-deals/1445983/