I write using Markdown, which can easily be converted (through John MacFarlane's excellent Pandoc) to formats such as .docx or PDF (through LaTeX). My Markdown editor of choice is Byword* (which is simple, clean and free from distractions).
If you're interested in trying this out:
(i) Download the following: Byword (if on Mac, otherwise, a different Markdown editor), a LaTeX package (e.g. TexShop/MacTex), and Pandoc (which runs from the Terminal).
(ii) Create a document in Byword and include the following metadata at the top of the document (separated by three lines on top and bottom):
title: "Your Title"
abstract: Your Abstract
author: Your Name
bibliography: [insert here the filepath to the .bib file that is your bibliography file]
fontfamily: Minion Pro