Re: What must be added...
Regarding the documentation. I don't know your background, but it sounds like you've been working with MS DX before, and not OpenGL. Moving from DX to OpenGL would be a pretty steep learning cure, I would assume. All the good documentation and samples is to be found on OpenGL side, not OpenGL ES. Basically the only doc needed for ES is what is supported and what not, compared to the full OpenGL.
If you want good understanding of OpenGL, buy the book: "OpenGL Programming Guide" also called the red book.
For me it was like this: After not knowing what OpenGL ES is, it took me about 5 hours to find out and port my old 3D engine from OpenGL to OpenGL ES. OK, not all features, but most of the functinality. So I would say the documentation is quite okay for ES.