I have been asked for my AP every time but once. Many here will tell you that you won't have to show the card...but, do you want to take a chance like that? I was in line to checkin at the CR once..there was someone next to me checking in as well. They had booked the AP discounted rate. They told the CM that they didn't have their AP yet...they were going to get it as soon as they checked in. Since Hurricane Charley was on his way that day, the CM told this person they needed to get right over to Guest Services at MK since they were closing the park in two hours!!! She said that if they didn't come back with the AP before the next morning, the rack rate would be charged. I've heard of that from other reports as well.
CMs are supposed to ask to see the AP card. I almost wish that you have to book your AP discounted rate online, through the AP website. But, that would make it hard for those who don't have the AP in hand yet. But, at least it would cut down on some abuse.