Thanks for the link. Appreciate the amount of work that has gone into this, very well done to the author(s), super work.
Stunning attention to detail - font choice on install, dynamic file renaming, open file highlighting, tabbed windows with apps inside. These felt so intuitive to me as I watched. Vector based UI - excellent choice!
Watching the demo brought back memories of OS/2 and BeOS in terms of aesthetics and usability. The theme designer blew me away - it looked like Sketch or Adobe XD in terms of UI prototyping. If this offers a way to draw your UI with vector based tools and have it "attached" to the OS's API then that's really exciting.
Further, if this could be extended to a VB style application where one can code in actions, events etc in a user accessible way [1] then I think it would be a killer app for this OS where a user/developer could shape the entire OS to fit the needs of the design.
I'm thinking here of a single use OS on a USB stick - for example, a writer's OS where the whole OS/Apps just provide a rich environment for wordsmiths to work in creative isolation. Like the "Zen" mode of many editors, but taken to the next level. Glorious looking dictionaries, pinboards for notes and research etc etc. Design the UI, apps and utilities and compile it all into a single, bootable OS would be wonderful. That would be very satisfying to me the way my mind is wired.
[1] To be clear, a language which is approachable by beginners, e.g. BASIC like or some high level scripting language. Also pluggable languages would be very cool for advanced workers.