UPDATE: Added HTML Export. Need feedback on whether its confusing- instead of putting some dropdown or something, I just used the expedient of the selected file filter, i.e. if you choose PDF in the save dialog, it will export in PDF- otherwise it's HTML.
It's not confusing, but it didn't work on my system. Even when PDF is selected (which is the default option), it still saves it as HTML (and so does the HTML option). Personally I don't need the PDF option. Normally I print to PDF, and looks like CTRL+P does trigger the printer, so that's sufficient.
Clicking on the Information icon crashes the app on my system (Win 7, 64-bit).
Also, I had some encoding issues, with dashes, apostrophes, quotation marks and French accented characters being replaced by a dark square with a question mark.
I wasn't sure what the button before the close button is for. It didn't seem to do anything.
Otherwise it works fine, renders Markdown correctly. Aesthetically speaking, I'd prefer if it didn't justify paragraphs or at least the headings (i.e. align text left instead), as it makes the text look messy, by stretching it out (actually the paragraphs look fine, it's the longer headings really that are a problem).
But it's coming together nicely, so keep up the good work! Thanks!