Anything other than Word is a non-starter for 99% of law firms (and the other 1% is still on WordPerfect). Markdown is awesome and I use it for my notes files and all kinds of things but contracts, settlement docs, pleadings, motions, etc etc all exist strictly and only in Word. And probably 50% of those are still .doc format, which was left behind more than a decade ago in Word 2007.
This product, if it works, will be a God-send for firms like mine (small to medium litigation shops that don't use full document assembly software with built-in version control like the AmLaw 100 firms. And it looks like even those firms might profit from this solution if it plays well with their customer style sheets and macros.
I wish it were different, but sadly the state of legal tech is mired in the late '90s.