Sometimes the issue isn't too few features, but too many. A number of writers want simplicity above all else, so they can focus purely on the words. Dark Room is as simple as you can get without going back to a Smith-Corona. It has a window, and you type in it. A very simple menu bar allows you to load and save. If you prefer, you can go full-screen and see nothing but your words and a few icons to navigate up and down.
If that's too minimalist for your taste, Jarte adds a few more features. Built on the same engine that WordPad uses, Jarte provides an unconventional but usable interface and a lot of functions that WordPad doesn't have, such as headers and footers, tabbed documents, and quick links to handy Websites. (Those links don't seem to be user-editable, however, so there's always a chance that someday a linked site could be taken over by something unpleasant.) Jarte is free, but its creators also offer the $20 Jarte Plus, which includes additional features. Jarte can run from a USB drive, too, so it's nicely portable yet still feature-rich enough for many tasks.
Another open-source project, AbiWord, evolved from a Macintosh word processor to a cross-platform product. It isn't quite as feature-rich (some would say feature-overloaded) as Microsoft Word, but it isn't minimalist, either. Although it has a good set of features, I experienced issues with it, including installation problems with the Help folder as well as some Styles breaking due to hard-coded references to the Dingbats font (which is not included with either Windows or AbiWord).
Although not intended as a replacement for Microsoft's own Word software, Windows Live Writer is interesting because it serves a particular, but large, niche: bloggers. With Windows Live Writer, you can compose and edit items offline and then post them to your blog. I've experienced the heartbreak of losing data to back-end issues and timeouts that crop up after I write a long post in an online editor, so I can say that this is a very useful program. Microsoft is of course pushing its own Windows Live service with this application, but I use it for my WordPress blog, and I've experienced no problems thus far. (Obviously, it doesn't support any editing plug-ins that you may have in your WordPress installation.)
A Word Processor for Every Need