I am exactly in that Amex boat. Cleared the Amex waiver and based on flights for the rest of the year I would have been about 10k miles short of diamond. Booked sea-pek for 750 bucks. With the double mqm in Seattle right now it's about 21500 mqm trip and about 43k award miles. Doing the math, pay with miles with 40k miles takes 400 bucks off an upcoming flight. As I diamond I won't have to have a reserve card for skyclub access and can downgrade to the platinum card saving 250 a year. So this flight cost about 100 bucks without factoring in the other 2 choice benefits and better upgrade chances. So milegage runs still do make sense in the right situation plus I can explore Beijing for 2 days.