Typora is a refined and clean text editor, perfect for blissful writing of longer texts. It it markdown based, but without the usual annoyances.
– it hides the usual markdown code in favor of the live formatted view. No separation of "code" and "preview"! Still, it remains a fully functional markdown editor.
– it has a very nice & functional outline pane, hence making it ideal for writing longer texts, like research papers, books, etc.
– It has excellent import/export to several formats (using pandoc).
– The UI is beautiful, yet you can customize it with your own css, as well as typewriter/focus/source code/outline views, etc.
And much more. A bit similar to IA Writer or Ulysses, but better IMO.
The only draw would be that it is in perpetual beta, with no comments from the author as to what the final pricing, let alone release date, will be. On the other hand, it is pure markdown, hence nothing is lost by using it, you can always shift to another MD editor.