Author of Us & Them: The Science of Identity.
Scrivener is head-and-shoulders above all other Mac applications for writers (and I say this having tried every one over the past 15 years, and heavily using several of them). Scriveneris fast, it's reliable, and it's intuitive. More times than I can count, I have tried to do something in Scrivener because it seemed logical to me, without knowing if I could, and been pleased to see the result I expected. Scrivener makes it easy to keep track of everything that matters — research material, notes, multiple versions of drafts — while forgetting everything that doesn't. The application doesn't require you to think like the guy who wrote the software, or require a lot of your attention to work flawlessly. It lets you be yourself. The developer is amazingly attentive and responsive, too. And it costs a fraction of what its competitors charge.