Our youngest is on the autism spectrum and several several issues at Disney. We have not used the GAC on our pass trips. Mianly, for lack of understanding what it was until I found the boards. We do plan to use it in May, but we just need a quiet place to go through the lines without being packed in so tight for her. Since she can be helped through a line I have reservations about using a GAC, but we are hoping for a less stressful trip.
That being said, in Jan we were waiting in line for Goofy at AK. The line was short about 4-5 families so I hopped in with my youngest. She was doing great until another family came up with a GAC and bumbed in front of us (we had finally got to the front of the line). They had the child and then all 7 of the family members (4 adults) get autographs and photos. I do not mind a child with needs jumping in front of us at all, but as they walked away I had one of the adult women say I told you it would work - we can jump ahead anywhere now. Which made me think the child probally didn't need the GAC. Odd part is they were not trying to talk softly and semmed proud of their actions. The handler looked at me and sighed, but did not say anything to them. I guess cause a CM can not question a guest about medical issues.