"browser-based IDEs aren't new. But they've always been a beast of their own; this will work seamlessly with the tight VS Code integrations numerous languages and frameworks have."
Yes, I evaluated AWS Cloud9 and walked away, because it was obvious that it could never compete with the ecosystems of the major editors. New tools and frameworks will keep coming, and proprietary cloud developer environments won't keep pace.
This project or Theia[1] look much more viable, if they can maintain enough compatibility with VS Code.