I agree with both of these people that you should study and understand Scientology. However, I think that if his life is becoming better because he has chosen this as the church to follow, and it looks like there is no wrong doing, then, why try? You have to remember, that like these people are referring to it as a cult, there are MANY people out there who look at many religions the same way. Lets look at a definition of a cult: a cohesive group of people devoted to beliefs or practices. Well, that really puts so many things under that category doesn't it? Some things that cults do are thought reform, and love bombing (overwhelming a person with affection to "recruit" them). I think you can see where I am going with this (missionaries, God rallies, Peace Corps, etc..all examples of thought reform and love bombing). Just because Scientology is a new thing, it doesn't necessarily mean it is a bad thing. I would hope that your son did not go about lightly in choosing Scientology, and that you can look at his decision with an open mind before you try and run him away from it.
And if you are a Christian, "judge not lest ye be judged".