The main thing that separates MultiMarkdown from Markdown is that it has been optimised for writers, and the production of long documents which require such things as footnotes, tables, cross-references, glossaries, and bibliographies. There are a lot of great Markdown editors out there these days, but most of them are focussed on what Markdown is good at: web publishing. MultiMarkdown Composer, with its integrated table of contents feature, drop-dead simple table creation and editing (better, I dare say, than most heavy-weight implementations in Cocoa and most other word processors), and more will make for a nice semantic writing environment.

There are still some areas that could use improvement. Footnotes could be better. They could cross-link instead of requiring manual searching by the marker ID. They could also have a helper that generates an anchor ID, pastes it at the bottom of the document and lets you type, then easily return to where you put down the marker, like I developed a macro for in TextMate.

A few other little things would make it better, but rest assured this is a very solid 1.0 and for a limited time it's a steal at $8. One word of advice: make a demo. Fletcher might have my cash on the barrel without a flinch, but not everyone knows the integrity of his designs. A demo helps people make that decision, and with a solid piece of software like this there is nothing to fear in letting the usability shine for 15 days or so.