From what I've seen the diet works great in some kids and has no effect on others. In my opinion, the diet isn't the cure, but it eliminates one other distraction and variable in the guess work of autism. In some cases it makes for happier, healthier kids and happier, healthier kids are more able to focus and respond better to therapy and interventions.

Diet was not a cure with my son... no effect. But, what did help is local honey for sweets, essential oils and massage. Oh, and lots and lots of patience. Knowing when I am pushing too hard and need to back off and eating an apple and peanut butter will derail a meltdown overtime for him... protein and sensory crunchy.

The earlier the better! Trust me I have a 2 year old and a 15 year old in the spectrum and my toddler is looking at me, answering to me, babbling again, has 5 words and keeps trying! It took 1-2 months of strict off gluten, casein, soy, wheat, and dairy. He has breathing problems and not anymore since off dairy! lol... Anyways you have to start slowly and I post all items I buy and where on my pinterest account...check it out!
http://pinterest.com/lucybourque/
My 15 year old has like a five item menu he only eats so it is hard I am trying but the earlier the better!

the gluten free / casin free diet creates kids who sneak around and try to steal food from other kids and causes them to want to eat off of the floor.

There is nothing unhealthy about a GFCF diet. It is not low-carb (most whole grains are okay, as are all fresh fruits and vegetables) and calcium can be gotten from non-dairy sources. It was much less difficult to follow that I was afraid it would be.