I am going to use it only to buy tickets on Continental.com since I get 5% off on all tix booked thru Continental.com, plus double miles. I am planning to cancel it in Nov. before it renews again. I am in the process of getting a Starwood Amex to use as my main credit card.

The only negative consideration about keeping the Master Card and not really using it is that it has very sizeable credit line and that might count against me for credit scoring purposes since the more "credit" that is extended to me (taking into account this card and my forthcoming Amex), the higher the likelihood (in the credit agencies' minds) of me running up large bills that I can't pay....).