Reading through the comments so far and watching the demo, I think the video demonstration gives the unfortunate appearance that the ultimate goal of the block editor is a page builder like expierance. Particularly with the authors use of the add-on that adds all the additional font options. From my understanding or at least my hope, that’s not the direction of the core block editor ( not saying that plugins wont be built to give it that functionality ).

The real beauty of the editor is when it’s used with a theme that is setup and styled for the blocks so that content is added and automatically formatted, with a few options for variations. I assume like widget areas, there will be some way for themes to define and control block areas.

Another issues with the demo and the unified editing experience is something anyone working with the current editor and just post content will have experience, space limitation. The demo takes place with all sidebars and settings hidden. I can only imagine what the experience will be like for clients working on laptops with low resolutions screens. I think there is some value in separating out content areas. A unified view seems like a good idea, but separating out content and editing spaces ( all with the same editor experience ) can also be beneficial.