I did my own pondering on the value of a mile recently. I have both the AA Citicard and Chase Freedom (1.1% plus 10 cents per transaction) and came to the conclusion that $20+ is my personal tilting point for taking miles over cash. At that point my reward is either 32 cents or 20 miles, 1.6 cents per RDM.

There are other benefits though. What is the value of achieving lifetime status? Probably in the thousandths of a cent range per mile, but a trip of a million miles begins with a single iDine. I also like having the ability to travel on a whim with my "free" tickets.