Which word processor?

If you use a word processor on OS X, which one do you use and why?

I’ve been trying a demo of Nisus Writer Express, and I like it so far after a couple days of light use. But there are other word processors I haven’t tried and I wonder what you think of them.

Some people use Word because they have to. I have to use Word sometimes too. I’m talking about when you don’t have to use Word—what do you use then?

Also, most of the time I use a text editor (BBEdit), but sometimes you want or need a word processor.