Agreed. In the case of computer tools, I think the difference between someone productive using Word and someone using Scrivener is going to be pretty small in most instances. For the novel I'm working on now, multiple people are speaking (like Tom Perrotta's Election or Anita Shreve's Testimony), for which Scrivener is pretty useful. But for anything else I've written, I don't think Scrivener would've been a huge advantage. I'm not even sure it would've been a small advantage.
To carry this too far, I think the analogy demands that language/grammar/punctuation are the ingredients. They end up in the customer's mouth. The tools, be it edlin or a pear peeler, only make the chief/writer's job easier. You have to use good ingredients, but the tools are a matter of efficiency.
