The UI in the video is rough and there are certainly bugs to clear but the bigger pieces are there. Scroll is possible only because of HTML 5 , Chrome, and a hell of a lot of javascript but in some sense you could think of it as enabling an older kind of publishing. When you work in print and you're putting together an article, you start with a blank page and you start dropping text and visuals until it works. The same is true here.
If you'd like to get in touch: hey@scrollmkr.com