The thing that excites me is using the react component paradigm for non DOM stuff like canvas and webGL.
useFrame binds a single component to the render-loop. But in a managed way. Once the component unmount, it's getting taken out. You can also stack calls like that with something like a z-index, which is awesome for effects.
This game uses some of it: https://codesandbox.io/embed/react-three-fiber-untitled-game...
I haven't looked at the details for web, but I think it does webasm and canvas, etc. and with the architecture they have it could potentially be a lot faster than traditional JS frameworks https://flutter.dev/web