I hesitate to jump in to the conversation at this point, since I'm pretty sure we've all made up out minds already, but reading the last few pages tonight has made me sad (for lack of a better word).
I think many "non-disabled" posters are missing the point that Steamboat Wil made so well (I don't remember how to quote anyone. Sorry.):
"...That being said follow a special needs family when we go to the parks. EVERYTHING ELSE takes longer. It takes longer to go to the park being loaded and unloaded on a bus where everyone gives you the death stare for holding them up. It takes longer to transfer while in line. It takes longer for bathroom breaks. It takes longer to eat at a restaurant while loading or unloading. How about the people in bag check lines who have to explain their meds to security..."
Guests with disabilities effectively have less time than "normal" guests in which to visit attractions. It's fine to say "they can do Fastpass just like everyone else. They don't deserve anything extra", but in the eyes of someone with a mobility issue (for example), it's not really extra. It's adding back in the time that the disability has taken away from their day. All the time they spend on the things Steamboat mentioned, and sometimes just the extra effort they put into MOVING around the parks, can be made up by being able to avoid some of the waiting they would otherwise do at the attractions. GAC cards help to level the field for these guests. It's hard to see it that way when you don't deal with health issues on a daily basis. It LOOKS like someone is getting something you're not. But for families who do deal with these issues, it can sometimes be the only way they can have a family vacation.
Does it go "above and beyond" what the ADA requires Disney to provide? Sure. That's what Disney is famous for - those little touches of "above and beyond" are what brought most of us here in the first place. Now they have to walk a fine, ever changing line between providing a very significant service to one segment of their guests without alienating another.
On a personal note, I wish some of us would please remember this is a very personal topic for many people, and these discussions will be far more meanigful if the conversation doesn't get nasty. Put yourself in the shoes of whoever's on "the other side".
Edited because Dasnowz said it before me AND better. Dang.