While most other blogs are talking up American Express cards, personally, I have yet to have experience with them as what is in my wallet is Discover Card. I personally primarily use a combination of my Discover More and Discover Miles cards for all purchases. My wife uses a Discover Miles card. While we may not be earning more than 1% in either cashback or miles on each of the cards, except during the rotating category periods, the Discover Cards are our longest running cards (it was my first card). In addition, some of the Shop Discover deals are always at the top of the pile, specifically Groupon, which we most often use.
Discover® More Card has extended their offer through the end of the year where new accounts receive a $150 cashback bonus after $1,000 spend within 90 days. In my history with Discover, that is an excellent offer, and far more than we ever received back in the primeval days of zero or very little credit card bonuses.