I've reviewed plenty of simple text editors designed for writers. For my writing, I really desire only a few features:
Support for plain text.
Running word count.
Oddly enough, the last item is the most difficult to find. In fact, most text editors don't have a running word count, even though that's the metric most writing is measured by. In fact, the editor I'm using right now, from http://is.gd/writebox, didn't have that simple feature when I first started using it. I e-mailed the developer, and within hours, the feature was added to the application!
If you followed the link, you'll notice Writebox is a Chrome application that runs completely inside your browser. Because it's a Web application, when the running word-count feature was added, it instantly was available to all users. If a text-only editor with Dropbox syncing, off-line support and a running word count sounds like the text editor of your dreams, check out Writebox.