Creative Writing Through Tools

Programming text editors are a dime a dozen, quite literally: there are dozens of great, free open-source editors running from vim and emacs to full-fledged IDEs like Eclipse and Netbeans, and it’s pretty understandable that developers would spend time building tools for their own craft.
But I recently discovered that there’s a set of mac apps designed for solely writing. I went and tried out a few, intrigued by what a designed writing experience offers.

Of course, the facto editors TextEdit and Textmate (and its spiritual successor Sublime Text) are perfectly capable if slightly ugly text processors. Textmate in particular has built-in bundles for Markdown, which come in handy for the occasional syntax highlight; otherwise, it is at heart still an editor optimized for programming workflows.
I discovered Mou when searching for a Markdown-specific writing pad. It’s a dual-pane editor, one side with meant for typing while the other provides a live preview. It’s nice to get a high-level visual representation of a piece of writing, but in its current state – a free piece of beta software – its features are somewhat limited. It also wrinkles a bit that Markdown’s main appeal is readability without parsing, but instead of inline highlighting Mou decided to provide a completely separate “rendered” view of essentially formatted text.
Next up is OomWriter. The developers have an interesting take on writing: the app takes over the screen and the speakers, and is meant to instill a sense of zen to allow writing juices to flow. I was skeptical at first, but after writing a few paragraphs at work I’ve found its purposeful limitations to be helpful in blocking distractions. This app is legitimately free (with a more options paid version), but its quality compares to any paid piece of software{{1}}.
And one I’d like to try is iAWriter/Writer. The design philosophy behind this one is minimalism, taken to its natural conclusion; the result is a blank editor that has absolutely no options save the ability to go full-screen and highlight one sentence at a time. The developers boast about the exact size of the fonts and space between lines, and I suppose I’d be ecstatic if I shared their aesthetic taste, but I’m not so certain that what they find to be perfect is universally applicable. It’s certainly not a writing tool for everyone, but I’m a bit curious whether such meticulous design makes for ultimately better writing.
What other tools have you used and liked? Do you find that these editors, minimalist or otherwise, actually improve your concentration and quality of prose?
[[1]]The gentle key squeaking grows on you. Really.[[1]]