If, using LaserTag's math, each MyPoint = 0.20 of a mile, and each mile is valued at $.02/mile, then 1 MyPoint = $0.004.
If you take a look at the MyPoints reward charts, many of the $50 Gift Certs (like to Home Depot, Hyatt, Spiegel, and others) for 5,250 MyPoints.
So, using the math above, 5,250 MyPoints * $0.004 = $21.
Therefore, in my humble opinion, you are better off going for a gift certificate rather than the miles..... (oppps, did I really just suggest that???)