It is really simple. Collect all your cards in one. Digitally. This is essentially Coin. Next step of course is that you will just have them on your phone. But this is a nice first step for now.
Having worked for a lot of banks I wonder what this will do to the top of wallet issue. This will definately eliminate or at least diminish the badge value of a card like AMEX over say Citi. Very interesting.
But most of all a great utility.