I've actually has taken a Silva Method course (although not one of the official). I've also read some books. It is not a cult at all. Silva Method was developed during the 1940ies by Jose Silva who was a simple man from a hard-living family in Texas. He became interested in psychology during army and being a person of high learning abilities wanted his children to study as well as he could.
So he started to experiment with them. First he used hypnosis. His hypothesis was that a person's IQ could be improved. But hypnosis wasn't good enough for him since it required the "second man", who leads you into hypnotic state. He became interested in the brainwaves research and have found that the alpha state (7-14Hz) is very good for studying. So over time he developed a method so that people could enter alpha state on their own.
It is actually very similar to meditation + visualization + intention manifestation. In the alpha state (during the meditation) there are some techniques that allow you to better "program" you for success/health etc or reprogram from bad habits etc. It's like a toolbox of meditations for various needs.
I've had some success with it both for healing some of my problems and for reaching my goals. Overall I would recommend it.
You can read more about Silva Method on my site on
Silva Method category.
You can also read an interview I've done with a man who is using Silva for a very long time and very good at it:
Interview with Larry Plato - Jose Silva Mind Control Method and Silva Ultramind expert