Come in, LightPaper. Easy file access via the sidebar, multi-tabs, script assets, Jekyll Rendering, Math Rendering, MultiMarkdown or GitHub Flavored Markdown, a preference tab where you write CSS for extra customization on top of the usual CSS-based themes, and much more.
I haven't really got accustomed to the usefulness of Shadow and Scratch notes, but so far I'm really pleased. Plus, their support is ace: my trial expired and their licensing provider doesn't support trial extensions / resets, but they went a lot out of their way to help me out. ==Kudos!==