I don't remember Vim's Markdown support to be anything special, either; I do a lot of Markdown work, and tended to use Markdown-specific editors on the Mac like Ulysses and iA Writer, while doing my technical writing in BBEdit. (I never found Vim to fit me particularly well for prose of any kind, even though I was pretty experienced with it. Apparently my writing brain is not modal.)

Semi-ironically given the Org mode discussion, the markdown-mode package for Emacs makes it one of the best Markdown editors I've used!