A big "Aha" moment for me was that I could just grep the big scary tar.gz source code of a project. (And that the big scary tar.gz wasn't that scary) Before that moment, I had to post a question to the project's forum or submit a bug report if I had a problem with a project. Then one day, all of a sudden, I realized I could just go ahead and grep the source myself and that the source wasn't scary. I realized that not…
Ummmm, any introductory book on Emacs or Vi would have a chapter on cross-referencing tools, specially etags/ctags. Do people really not know how to "dive into" code bases?
Maybe it has to do with reliance on IDEs? I've seen people completely lost without IntelliSense, etc., and they're usually not familiar with using tags or grep.