Brett Terpstra has released Marked 1.3.2 for Mac OS X (10.6 or higher), an update of his viewer for Markdown and MultiMarkdown files. It costs US$3.99 and is available worldwide through the Mac App Store in the Productivity category.
Version 1.3.2 adds RTF copy/export, word count for selection, readability statistics and tools, enhanced keyboard navigation and more. Marked turns any text editor into a Markdown editor, allowing you to edit when you like, where you like.
It can track changes in the file and update the preview automatically on every save. Marked allows for HTML export, printing, save to PDF, copying HTML source directly to the clipboard, document statistics and more.