It's okay for people who know what theyre doing
That said, There are a number of improvements that could be made to this app: The UI is confusing, and doesn't work well with the iPad in landscape mode. A side-by-side layout -- with the editor on one side and the render on the other -- is sorely needed for those of us editing with the magic keyboard, rather than with the virtual one.
TL;DR: It's okay. I like the compiled preview, but the interface could be more adaptive.