I'm pretty new to this board, but this is what I've gathered about the AP rates...
AP rates are released for certain times for certain resorts and rooms, usually a couple months in advance. For instance, the AP rates for July and August '05 check-in dates were just released. These saving are a flat rate discount: $25 off Value resorts, $50 off Moderate resorts, and $75 off Deluxe and Home-Away-From-Home resorts, but that can vary. This is off the "rack rates".
As for January, AP rates have been released for Jan-Feb (value season) for at least the last 3 years. The code has been released anywhere from October to early December. You need this code to call and book your room at an AP rate, BUT you do not need the AP in hand when you book (just when you check in). You also only need one AP for up to 3 rooms booked.
Resort savings are the biggest plus, but you also can get a 20% off dining card for $50 as well as other Disney savings.
Hope this helps!