I find myself wondering how much difference the feeling of speed makes for creating a "flow" state. It may be physically faster to achieve a task, but if there's a minor context switch between "thinking about what to do" and "mousing around to do it" that doesn't happen with the keyboard, with a corresponding context switch back to thinking about the actual task that all this moving the cursor around is part of... how much time do those cost?

How much of one's internal working memory has to be flushed of the image of what you're trying to create, so that you can visually process mousing through menus much more densely packed than anything back in 1989 when Tog wrote that reply?