I really like John's perspective on things, he can take a listener or reader from the most abstract concepts to the nitty-gritty without losing focus. He's a tremendous asset to the programming world.
I agree with the second part of your sentence. I have watched every single one of his talks, and while I find them entertaining, I don't think his brain-dump style of communication is appropriate for teaching/instruction (to clarify: I use his talks as a springboard for my own discovery, not as a terminal point to aggregate knowledge).
I disagree. See the above link for a lecture where he describes the difficulties in VR in a manner that anybody with minimal programming experience can understand.