We use to buy them at check in. You can get the DC discount and they are put on the same card as your room key and credit card so you only have to carry one card for all three.
We have AP's now and I hate having to carry them along with our room key/credit card. And they're paper to boot! Hey Disney, can't you do better than paper for AP's?! (shouldn't complain too much...they save us a lot of $$$!)