We bought them last year and managed 5 trips. Dec 06, May, Aug, Oct and Dec 07. I think it was like 33 days or something like that. So ya we felt we got our money's worth. We had the DVC discount as well though.
You also need to factor in if you are including the extras like waterparks etc.
We are on our second Annual Pass and we reckon that even taking 15 to 20 days in total makes it worth it (thats aside from the discounts you get with it like room discounts,free parking and flexibility of use)
We started buying them when they offered a discount for DVC's . Any trip over 10 days will may it worth it.....We average 24 nights per year (10 and 14 ....so it works out really well for us).
We don't have DVC but did annual passes for our last trip. We went last fall for 12 days. So far I have just returned from a girls' trip where I was able to use my AP for the hotel discount & my park admission, plus the other discounts. DH was satisfied as we also did the DDE from that and definately got our money's worth out of that. Don't know if I will be able to sneak in anything else, our vacation time is pretty booked up this year with non-Disney stuff...
If a good AP rate comes out for my trip in June ...I will buy an AP this year....I also want the DDE.
I've looked back at what has been offered in the past(AP rates) and even with the cost to purchase an AP I would still be ahead $100 just on the room. Plus, another $160 for the (half price) hopper pass that I won't have to buy.