for the past 3 years, we've gone to wdw in early may and oct. /nov. the crowds in oct/nov. are less than in the spring, but it shouldn't be bad assuming you'll be there AFTER all of the spring breaks are over (we normally go the first week in may, but this year we'll be there april 27th). we notice heavier crowds on the weekends (true for any time of year, though) in the spring, so we really try to maximize our weekdays. we've been there for the start of the yearly celebrations (happiest celebration), too, and that has made things crazier in the spring, too.
on our first trip (a few weeks after the kids turned 2), my dh got an AP to use the AP discount on the resorts as we had our 5, my parents, and my in-laws, and we all had diff. rooms. this discount alone paid for the AP. we thought that we'd go 2 times during that year while the kids were under 3 and FREE. well, we ended up going 3 times (mid-nov, may, oct/nov). we had SO MUCH FUN on those trips, that about 3-4 mths. after the kids turned 3, i couldn't stand the thought of not enjoying that magic some more while the kids still found everything so REAL and MAGICAL as toddlers (even if we DID have to pay for them!!

) , so on a bit of a whim (a very expensive one), we bought APs for all 5 of us and went in may, this past nov, and we'll be going 1 more time this coming april/may on these same APs.
already at 4, my kids are figuring out on their own who/what is real and pretend, who is just "dressed up in a costume", and what is possible and what isn't realistic in regards to all things disney. i do not regret for one second our decision to spend the $$ on these trips and not other things (well, ok, depending on how my 3 are behaving on some days, perhaps i have moments of internal struggle

)...we have no babysitter, we do not send them to preschool, we don't have lots of new stuff for the house, etc., and the majority of these decisions are based on the fact that we want to spend our money on vacations together.
dh and i traveled a lot before the kids, and we dream of taking them to the places that we loved to visit together or the places we have yet to travel to together:national parks out west, to australia, to the scottish highlands, to the east coast.
realistically, though, most of those places would be VERY difficult to travel to with 3 little ones, not to mention very expensive. WDW allows ALL 5 of us to be happy at the same time, doing the same things together, for a very "reasonable" price (given the quality and quantity of the entertainment and service), almost all day long ...and with three toddlers that is REALLY saying something!!!
so to answer your question , for us, yes, absolutely, the APs were worth it...it is cheaper to get an AP than buy indiv. tickets for 3 8-9 day trips in one year (every 6 mths). in addition to that, we have saved hundreds of dollars on resort costs by getting an AP discount on the rooms that we have stayed at on-property for both us and others travelling with us.
beyond cost, the AP has been worth it for me, as a sometimes overwhelmed SAHM, to have an incredible vacation always "in the works" and on the horizon, kwim?
we really noticed a difference in the kids' attitudes about WDW this last trip when they just turned 4...they were more interested in rides and going on to the next thing, as opposed to every other previous trip when they have just truly enjoyed being in the moment and enjoying the infinite little details of the parks and resorts. we really felt like something had changed, and a bit of that little kid wonder is gone

we assume that we'll start exploring some of the other amusement parks closer to us over the next few years and visit WDW again in a few years.
take care,