One catch with Capital One's program is that you can't use points to buy part of a ticket (for example if the ticket costs $600, and you only have enough points to pay for $550, you're out of luck - they won't buy the ticket for you and allow you to pay the remaining $50 in cash). Other rewards programs do allow you to pay the excess in cash.
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Also, in my experience, Capital One's customer service is highly unresponsive.
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I suggest checking out Zion's Bank and Wells Fargo - both offer programs with points valued at about 2 cents each (example - 25,000 points for domestic RT up to $500; if ticket costs more than that you can pay the difference in cash). Both have various restrictions, but may be a good complement to regular FF miles.