I started DS 4.5 on GFCF in June. He has ADHD combined and has some traits that put him on the ASD spectrum. It has made a HUGE difference!
I HS my older DD and always dreamed of HSing my two little guys (also have a DS that's 2). DS has about driven me nuts, literally. In the spring we had him observed to start the IEP process, he got up 17 times in 30 minutes while a "behavior specialist" oberseved him in a preschool setting. Last week she observed him again for four days and the most he got up in the same time frame was 5. He doesn't qualify for an IEP on behavior. YEAH!!!!!! For the past month we've been "doing school" and he's been doing really good. This fall he is going to go to preschool for three afternoons a week and we'll continue doing school at home, hopefully next year for K he will be home full-time.
Basically we eat grilled meat, a vegetable, and fruit. He likes fruit snacks, GFCF pretzles, and GFCF ice cream for snack. He likes hot dogs, and chicken fingers breaded with corn flake crumbs for lunch. He also has fallen in love with baked potatoes with non-dairy "butter". We have noticed that our grocery bill is much higher now but we hardly go out to eat anymore and fast food lunches are completly gone, as are snacks from the bakery orgas station, so we are saving loads of money.
Sorry for the long reply, I could talk about this forever. Bottom line, it is so worth trying and you have nothing to lose, and a lot to gain if it works. :)