I used Scrivener to write my 2010 Nanowrimo entry. It's a great piece of software, and I can't recommend it enough.
The main reason I say is because I think a lot of people, based on the amateur writing I've seen, don't need a fancier way of arranging words so much as they need to focus on 1) the quality of their sentences and 2) how one event drives another in their plots. I worry especially regarding point 2) that Scrivener lets people work in parallel when they should be working in serial, with one event driving another organically. Too much amateur writing I see is, for lack of a better term, plotless: meandering around feelings, or random encounters, or designed to show how deep the author is—instead of telling a story.
Scrivener will help with some things, as I've written elsewhere, but I'm not sure it's really enough for the vast majority of what writers and would-be writers are working on.
If you want to be a good writer, concentrate on your craft instead of your tools.
Tools don't substitute for skill, but skill with the wrong tools is wasted.
Still, if you're curious about this sort of thing, I wrote in more depth about it here: http://jseliger.com/2011/08/11/how-to-be-a-faster-writer-don... .
Writers figure out what works for them and stick with it (my wife used AppleWorks forever; George R.R. Martin still uses WordStar on a DOS machine.) Programmers similarly establish their preference (which is why over-30-year old text editors like emacs and vi have such strong adherents).
The original off-topic message in this thread was about how people continue to write poorly, even after they have great tools.
That doesn't surprise me at all. The hard part is learning the craft. For most people, it's also not a lot of fun. It's a lot more fun to "look for the right tool."
So that's why it takes a decade to turn out a new book.
That's 1800 best-selling pages in 11 years. Not too shabby.
You see the same pattern with amateur photographers, who think buying a nicer camera will get them better pictures.
Many good programmers do very well with old, free tools that have been time-tested and improved. You don't need Visual Studio Ultimate-mega-edition, though it will certainly make your life easier in some situations.
To use the chef analogy again, you wouldn't say "sharp knives don't make you a good chef, therefore use dull knives."
You'd say, "focus on learning to cook. Don't spend 4 hours a day looking for the world's sharpest and most durable knives. But yes, do get some reasonably sharp knives. Then carry on with the chopping."
I just finished a novella using it. I didn't use all it had to offer, but the combination of index cards for simple and quick outlining and the full screen mode make it essential for me.