@Christina Warren - frankly, TinyMCE is bad, but I haven't used a better WYSIWYG editor before. I used FCKEditor (now CKEditor) few years back, but it was buggy and led to regressions for some of our sites. Fact is that there are millions of ways to bend a UI editor, switch to code view back and forth, drag some components, delete, save, revert, open a few tabs of the same screen, which isn't trivial to handle.

As for the styling - there are different flavours of Markdown which is also good to mention, as it's still a bit annoying (although not really a critical issue). And there have been limitations in embedding it within HTML, and some general use-cases from the practice. Getting used to the right indentation practices for code, bullet lists, etc could be confusing for people, using underscores to emphasize a file name with underscores could be just as surprising, etc.

I believe that it's a great step towards making people comfortable with Markdown, and getting many bloggers used to it. I would just like to see the results of a month of Markdown usage by a few thousand bloggers and their feedback, too :)