nicely done

There are things on my wishlist for WP-Markdown, but it works quite well.
In general, I find writing in Markdown a faster & more productive experience compared writing in the visual editor (or even with the text-only editor). The idea of duel-viewing your post (markdown & actual rendering) is useful, as you can check your work.

It would be even better to have support for a few things, like highlight.js included for writing code in blogs ??