Recs.
Updated
SpecsUpdate
Pros
Pro Great Markdown support without being intrusive
Byword de-emphasizes the syntax itself while emphasizing its effects. It appropriately adds style, like italic and bold, to text that's designated by markdown and dims the syntax so it does not get in the way of comprehension. Additionally, there are commonly used hotkeys (⌘b, ⌘i, etc) that can be used to apply style without having to know the syntax or having to type it out each time.
Pro Extremely simple
Byword is as simple as Markdown editors can get. Even though Markdown itself is not hard, Byword offers assistance to make it even easier with very little configuration required.
The UI is minimalistic and un-intrusive, the syntax auto-completion is excellent, and there are multiple small but helpful features that make writing Markdown with Byword a breeze.
Cons
Con Limited customizability
One of the things that makes Byword so easy to use is the fact that it needs very little setup and option-tweaking. However, that severely limits the ability to customize the editor itself. For example, there are only two themes available, a light one and a dark one.