Delta miles are darn near worthless at this point (well to be more exact I value them at about half the value of just about any other US carrier's miles) and the only thing I have found halfway decent value with them is using them to "pay with miles" on your credit card, making them worth 1 cent each. So if you plan to do that and to redeem all of the miles you earn before you cancel the card, then the miles are worth slightly more than the credit. But either way you are getting something for nothing and yes, it is a very good retention bonus. In fact they offered me almost nothing, a $25 credit I think (but I spent nowehere near what you did on that card). Now without the card and ability to use the miles for .01 each, I am getting out of the Delta miles business altogether. Not worth the trouble.