I look at IDine this way:
If you spend $4000/year, you can get 20% cash, or $800, or 40,000 miles, worth an upgrade to Europe valued at ?$5,000.
If you spend $10,000, you can get $2000 cash or 100,000 miles, worth a ? $12,000 first class ticket to Asia. There is no fee for the airline program. I prefer the miles.