Improving your editing skills (one of my glaring weaknesses) are a near-perfect example of sharpening the saw. You already use an editor, now you're learning to use it faster.

I guess if we're going to play with the metaphor, learning to use a bicycle is not sharpening the saw, it's learning to use a new and better tool.

So if we go with editors, learning to type faster is sharpening the saw, just like training to walk faster. But switching to Emacs is like learning to ride a bicycle where you used to run.