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The Citi AA MC is certainly a great deal, and the card can be churned for multiple bonuses, if you wish. But if you want to keep the same card year after year, there is that pesky annual fee after the first year.
If you don't want to pay an annual fee, and you like to ride the rails, you might also consider the Amtrak Guest Rewards MC offered by Chase. No annual fee; earn 2 points per dollar on Amtrak purchases, and 1 point per dollar otherwise. AGR points are redeemable for Amtrak travel (3,000 points = a one-way coach ticket in the Northeast region, e.g.)
There's usually a 5,000-point sign-up bonus available for getting the card. Go to
http://www.amtrakguestrewards.com for more info if interested.