The field of personal development is littered with charlatans so it has been my experience that it is entirely worthwhile for anyone that is exploring it to explore the skeptical side of it as well.
In the attached clip towards about the middle of it there is an interesting demonstration where the psychic that he is conducting the documentary on is shown to be reading someone and then Derren is put on the spot and asked to conduct a 'reading'.
I found it very interesting that Derren acknowledged that wasn't psychic and only using the skills of cold reading was able to put on the demo that left the person that was the subject walk away and claim that they thought Derren in fact was.