Wood Nymph, focusondisney, and Hopper Fan, thank you for your detailed responses. It sounds like you have to be flexible in dates and resort choice inorder to maximize the benefits of an AP.
Yes, in order to maximize the benefits of the room discount, but the AP's main benefit is being able to go to the parks--and park hop--for more days than you'd be able to if you purchased park tickets separately for each trip, assuming you're planning on going to WDW and to the parks at WDW for more than maybe 11 or 12 days a year (this depends on what your dates are, etc.).
And the AP room discounts, like any other WDW discount, is best booked the day or at least the week the discounts come out. After that, room availability isn't as robust.
BTW, IME, the bounceback discount is the best room-only discount at WDW, although for my upcoming trip in July, the AP discount was, for POFQ, exactly the same as the AP discount.
Something else to keep in mind: You can book an AP discount and then later want to maybe add a day or two to it, but those days may not be available at the AP discount. This is true of any discount room booking, btw.
Edited to add: If you want to see what previous AP room discounts were and when they were released, check out
mousesavers.com, where you can see all the particulars.