Getting an AP for a Deluxe is most often worth it. I just booked the Fort Wilderness cabins for April 2 - 7, total AP rate, with tax, $1092.75. Had I booked full price, the cost would be $1778.50. I also checked into
AAA but there were no cabins availalbe with AAA rate for these dates. Even so, at the normal 10% discount, I still save with the AP.
Adding the cost of an AP, including tax, of 442.00 to the AP FW 5-night cabin rate brings the total to $1534.00 for a total savings of $244.00 over full price booking. In this case, it was well worth it and if we choose not to go to the parks at all or actually use the AP ever, we've still saved.
Previously, the rule was 8 days minimum to get value out of the AP but my math tells me otherwise. However, if choosing a Value or Moderate resort, the savings is a bit less and this may not payoff.
My advice is to call Disney CRO and get the AP rate for the resort where you want to stay and do the math. It may surprise you.