Rated 5 out of 5 stars

I like the idea and the extension's features. :D This does not only allow you to use Markdown but, as a consequence, also free-form HTML code which you can quickly turn into the "real thing" even in Gmail (which by default does NOT allow HTML). It also has the feature of customizing the CSS of the rendered markup, which is awesome if you want to give it a unique look.

This review is for a previous version of the add-on (2.9.4.1-signed).