When we were there in 2012 with our then 3 year old son on the spectrum, we did bring a letter from his doctor that stated what accommodations he would require to be able to function as a "typical" child. And even though I had it, Disney did not want to see it. They also willingly, and lovingly gave us our GAC and explained it to us. It worked then just like an unlimited FastPass, or at least thats how we used it. However, we also agreed that if the line was less than 20 minutes, that we would use the standby que. He did very well with this. The only major meltdown that we had due to the lines was while waiting for Buzz and Woody, which was close to an hour.
We are returning in May. Our son is now 6, and his tolerance is much better IMO. Does he still have meltdowns, yes. Does he still have issues waiting for long periods of time, yes. Will he more than likely have issues with the amount of people in such small places and most certainly the smells and sounds associated with that, of course! But why should that deter us from having a family vacation at Walt Disney World? As his parents, it is our job to expose him to these kinds of things and bring him out of his comfort zone. Will it be beneficial for us to pick up a DAS on this next visit, and have it for times when the lines are just too long to manage? Surely. But this is HIS vacation too. He should be allowed to escape some of the hum-drumness of his life just like the rest of us and actually enjoy himself. So if getting a "fastpass like" return time by using the DAS and going to wait somewhere that won't give him a sensory overload will help, then I am all for it.
I do not feel that Disney has ever discriminated against my son or my family. We have been overly accommodated on every visit to the World. My family would still attend WDW even if something such as the DAS or GAC was in place. There are so many other ways to enjoy yourself at the parks that don't require you to have to wait in any line at all.
I do want to say that I am appalled at some of the comments that have been made on this thread today. A little research on Autism and other developmental disorders would would do some of you some good. Maybe offer a little clarity into the reasoning behind the "special treatment". Anytime I hear about or read about a discussion such as this, it seems to always boil down to one thing....jealousy. "Its not fair that so and so with xyz gets to have special treatment when I have to wait like everyone else." And my response is always the same. My son has asked me numerous times why certain things bother him the way they do. Why people look at him funny or why we (his family) don't feel sick when we smell certain things. I can tell you for a fact that he wishes he could be "normal" and wait in an hour long line just like everyone else. The problem is most of the time he doesn't even understand why he can't handle it. He is a smart kid, and even at 6, he can see that the world treats him differently, and that he is different in the world.