where's it mentioned on that link? I can't seem to find hallucinations (don't worry found it).

Yes, sometimes its wrong, most times its right, cross checking is fairly easy, not using it because of the possibility its wrong seems a baby with the bath water thing.

I learnt a lot of functional programming from it, stuff I've always wanted to learn, but just didn't have the time and really the sources can be difficult, it really explained things well, and as someone else said in this thread, you can ask questions over and over until you understand, asking a person that (if you can get an expert) would drive them nuts. Maybe my experience isn't typical, its hard to tell, everyone reports something different.