It's also useful for teaching new features. If you are mindful of the existence of achievements, you might check the list once in a while and see something like "Fast Copy - Use Ctrl-C to copy something instead of clicking on the button!"
You'll soon run across things you don't take advantage of (it was registers and org-mode for me).
If you like this approach, I've written a guide (http://david.rothlis.net/emacs/customize_c.html) which, at 3,000 words, is half the length of the Emacs manual table of contents.