Also, there are a bunch of editors for writing Markdown for most platforms and few (any?) for ReStructuredText.
Really - I don't get this impulse at all. From my perspective, the entire point of markdown (and RST I assume, though I haven't used it) is that you can easily read and write it using any plain text editor.
If you are going to need a specialized editor to write it, you might as well use html, docbook, docx, odt, troff, rtf, or any of the zillion other formats.
- Key bindings
- Syntax coloring
- Toggle preview within the editor
I found Markdown generally had much wider support than RST.