For instance, I like block diagrams -- those are way too time-consuming to do in a text file.

Well, now that you mention it, I'm pretty good with emacs picture-mode too, but your point is taken that paper has it's own advantages. I'm not saying it doesn't.

(I am not, for example, a PDA kind of guy: I've always got a moleskine in one side-pocket, and a slingshot in the other).