I'm becoming more of a fan of points-based programs, the latest fave being FlexPerks (the thing U.S. Bank did when the NW/DL merger left them without a mileage-granting card).

Pros with FlexPerks:

* each point worth up to 2 cents (20K = ticket up to $400, 30K = $600, etc.)
* no redemption/booking fees and you get $25 reimburseable allowance for airline junk fees, food, etc.
* a standing double-points offer on certain purchases and occasional promos to really boost the total.
* Free tickets count as paid tickets, so you can get upgrades and they earn miles (this is huge, especially for elites).

Cons:

* No cash + points option. You can't use the 20K for a $400 credit against a $500 ticket and pay the extra $100. You have to book entirely with points at 20K minimum, so chances are you're not getting full bang for your points. (You *could* redeem for a travel cert, but at a less generous 1 cent per point)
* Points expire 5 years from when they were earned, if not redeemed.
* Would seemingly be easier to devalue or otherwise "enhance."

Basically if you're a travel-shopping and deal hunting junkie and you love to travel and can plan it to maximize mileage return you can do very well with a points-based program, albeit at a real cost in research time (as always) to bag the deals.