With the use of the "Sam's Club Hack", see post below, my Discover card has officially been retired to my financial papers box. You were an innovator Discover with your cash back, it will be sad to see you go. However, I can find NO opportunities where it is optimized to use Discover anymore.
However, do not close your Discover account for the following reasons:
1) You credit score is increased the older the average age of your credit cards is so obviously if you close old accounts this hurts.
2) Your credit score is increased the lower your debt to limit ratio is so by closing an account you hurt this ratio.
3) You never know when they might offer you a 0% deal.
4) You never know when they might start offering competitive rebates again.