Ranked in these QuestionsQuestion Ranking
Pro Allows customizing output
A custom CSS can be added to the rendered HTML to change the preview and output.
Pro Real-time HTML Preview
MarkdownPad is split in two panes. One pane is used for writing Markdown, the other shows the rendered HTML as it's written.
Con Many features are disabled in the free version
Free version lacks features like auto-save, PDF export, Markdown tables among many others and can't be used commercially.
Con Abandoned project
Nothing from author since 03/15. Pro version preview pane crashes, no fix has been offered. See user forums.