Kids get better even without therapies or treatment. The higher the IQ at the time of DX, the better the outcome. Even when kids lose the DX of ASD, they have on-going deficits that have to be worked with or around.
More on that here:
http://www.psychologytoday.com/blog/making-sense-autistic-spectrum-disorders/201008/017-losing-the-asd-diagnosis-does-not-equal-cur
ids and not others, or they may be attributing natural improvement to their interventions. I think the second is more likely, personally.
What does work? ABA, speech therapy, occupational therapy are the standard therapies and they are effective.
There are some alternative treatments that show promise. SA did a study that ranked alternative treatments:
http://www.scientificamerican.com/article.cfm?id=alternative-biomedical-treatments
They also did an article on dubious treatments. It's available here:
http://www.scientificamerican.com/article.cfm?id=desperate-for-an-autism-cure