The main thing that makes Scrivener so great is the way it allows a writer to break down a big project into its component parts. Using Scrivener I can organize my work by scene. I can easily move scenes around. I can insert scenes. And I can see the way the scenes fit together. I can edit two scenes simultaneously.
On my freelance writing blog, I'm writing a series on how to write ebooks FAST.
At any one time, I'm writing at least four ebooks. One for myself, and others for clients. As you might imagine, this could be confusing. Thank heavens I've got Scrivener to keep everything straight.
I've been using Scrivener for years now. There's no way I could manage handling book-length material for many different projects, all at the same time without it.
Scrivener's the one application which is always running on my computer. When I'm out and about, I've sent up iPad apps so I can pull them into Scrivener.
The above article gives you some wonderful ideas on using Scrivener for fiction.
I use it everything, including blogging and copywriting projects.