It certainly looks from the extension API docs that this is a thing the world needs - a modern GUI shell that allows arbitrarily complex extensions to be written in a language people seem to like. Having looked around the docs as a very heavy emacs user, I am not totally discouraged - every keypress seems to point at a command, and if everything is rendered as HTML, I assume it is effectively infinitely customizable (would love to hear opinions from experienced extension authors). If, on top of that, it solves a lot of emacs' foibles, like threading issues, performance edge-cases etc, then I plan to keep an eye on it.

That said, the available extensions seem pretty bare. I don't see many mentions of REPL interaction, and there are no extensions for many languages. I'm glad it's getting attention, but I suspect it'll take a decade of loving care to bring up to the level of most people's emacs configuration. I see no reason that couldn't happen more quickly, though.