I opened a few files. Really fast. What I like a lot is that I can open a whole folder and jump between the files very quickly. The included styles are very nice. I first had to get used to the fact that the list order changes when I pick a style, and the chosen one moves to the top. PDF export is also very fast, and the PDF looks good, which is not a given.

I'm working on a private project where I need a good Markdown viewer, and I'd like to take some ideas from yours. Our current file viewer looks amateurish next to it.