I can't speak for the other credit card programs... but, I take FULL advantage of my Membership Rewards points w/ AMEX by using them to partially pay for airline tickets. You book the ticket on AMEX's travel site (it usually has a slight service fee) and can "pay" with points... points are valued at 10,000 points = $100. Use as many or as few as you want to "pay" for your ticket.

The point equivalent shows up as a rebate on your credit card statement, with the full ticket price being charged. So, the airlines think you are paying for the ticket... and, therefore, you earn full mileage accrual.

To make it better, AMEX credits you 20% of your points back. So, really its 8,000 points = $100.