Although I'm not blaming the developers by any means since they've done an excellent job of creating all purpose, easy to use text editors of their own (such as Gedit, Kate, Leafpad, etc) but as said since the needs of a "true writer" is a bit different than with most of us, thus most of these applications may not simply meet your needs.
Now I've already talked about an excellent one recently which is known as Pyroom but it lacks few things such as no built in spellings checker and other few advanced options. But that being said, if you're looking for a very minimalistic writer app then it's pretty darn good.
But if you're looking for a much more closer to professional writing application for GNU/Linux, then Focuswriter (written in Qt toolkit) is simply an amazing application.
|This is in the "windowed" mode... by default it runs in Full-Screen...|
*. Not just for GNU/Linux actually, this is a cross-platform utility thus you can use it under MS Windows, Mac OSX as well.
*. Has a built in spell checker which as said something that most other applications don't have these days.
*. Find and replace text.
*. A lot of built in text editing features such as - screen alignments, add smart quotes, bold/underline/italic/strike through/, change font, size and colors + redo/undo, etc.
*. Switch between full screen and windowed mode by pressing the "F11" on your Keyboard.
*. Customize the look-n-feel by changing background colors, font colors, etc.
*. Few built in language support.
*. Printing support.
*. Save in different formats.
*. Add a third party dictionary.
*. Save text automatically (you'll have to enable it via the "preferences window").
*. It can even output typewriter sounds! :)... these are just a very few of its features to mention.
You can install Focuswriter in Ubuntu 11.04 Natty Narwhal, 11.10, 10.10 and 10.04 by using the developer's personal PPA. Just open your Terminal window and enter the below commands.
sudo apt-add-repository ppa:gottcode/gcppa
sudo apt-get update
sudo apt-get install focuswriter
In Unity desktop you can search for "focuswriter" or put it in your command-line OR from the main application menu go to: "Applications" -> "Office" -> "FocusWriter". That's it!.