THINC  This is the one. Like many of the other reviewers here, I've been searching for an app that supports my writing style for many years. I've tried them all (at least I think so). If you're a writer, you know that standard word processors just don't cut it. They are either too directive (with spurious "help" resources) or they've been designed to be everything to everyone or they bog down on long documents. If you're a power writer, you know what I mean. Most WPs just get in the way.

Then there's a breed of outliner/database/clipping apps that have appeared. Some are excellent. Devon, Mori, OmniOutliner, among others. They're not bad for collecting and organizing data, but they're not robust enough in the text handling department to be really useful as writing tools.

Finally, there are a bunch of folks (almost all of whom are writers themselves) who threw up their hands and realized if they were going to get the apps they needed, they'd have to write them themselves. The best of their output are Jer's NovelWriter, Avenir, CopyWrite, and Ulysses. All are dramatic improvements over what went before. But none can hold a candle to Scrivener. (For me, Jer's comes close, and I recommend giving it a try, but Scriv is just more my style.)

Scriver is rock solid. I've been using it since beta 4 (usually 3 to 5 hours a day on a complex project), and it hasn't let me down yet.

It has some blow-away features such as Edit Scrivenings, Snapshot, Annotations, integrated outlining, Corkboard, an outstanding full screen mode, and excellent import and export capabilities.

Scrivener's author is responsive, smart, and a joy to work with. The community that's developed around Scrivener is helpful and knowledgeable (not only about the apps, but about the world of professional writing).

I could not recommend this piece of software more highly. When I drive, I drive a BMW because I love its power, its safety, the way it handles the road, and its responsiveness to my every driving need. When I write, I write with Scrivener. Take it our for a spin. Put it through its paces. You won't want to write any other way.  
(Version 1.0)

THINC  Jesse Grosjean's WriteRoom is a first class app that doesn't do much — except totally transform the writing and note-taking experience. I was skeptical at first. I mean what's the big deal about writing in a full screen environment that looks like DOS? (Don't worry, you can change it to look like anything you want.) But within a few minutes of playing with it I was hooked. Writing was simple, productive, and yes actually FUN again.

But conventional writing and note taking are just the beginning. WR also has a game-changing feature called Edit in WriteRoom). With it, an EIWR menu item appears in all cocoa apps. Select EIWR, edit in WriteRoom's wonderful environment, then hit save and your text appears, as if by magic, back in your original document. Addictively sweet!

I use WR in conjunction with Mori (also by Hog Bay Software's Grosjean) and Jer's Novel Writer (a weirdly named but wonderful writing app by Jerry Segar a writer who'd had enough of Word and its kin) for my major writing projects, and I've never been more productive.

If you're a writer who's fed up with apps that get in the way of your work rather than actually help you work, all three of these are worth a try (both developers are also very responsive to user feedback).  
(Version 2.0b2)

THINC  I've noticed there haven't been any reviews of JNW for about a year. That's too bad, since many folks would benefit from trying out this terrific app. I've been using 0.614 for the past three months and putting it through it's paces. The developer's objective was to create an app that helped him write without the distractions of Word and Word-like programs, as well as to give him the organizational flexibility to track, edit, and restructure story elements. Even in this beta version, he has succeeded remarkably well. The program is stable and a delight to use. Anyone working on a longer document, who is concerned more with writing than formatting, would benefit by giving it a try. Jerry is also very responsive to user community feedback. The whole experience has been a pleasure.  
(Version 0.6.1.6)