tl;dr of 10 minutes video:

- All code uploaded to their orion servers

- Import of .zip files

- git commit and diff functionality

- Try your code with by running webserver username.orion.eclipse.org

- Syntax highlighting (at least for js)

- Use of JSLint for syntax navigation and error notification

- Keyboard bindings as you know them from desktop applications

- Handles huge files without any noticable delay (40000 lines+)

Oh and as I understood it, it is a beta and some functionality are not fully implemented, like the .git support.

Personally I believe some things are better of being a desktop application - and do not like the trend with _everything_ on the web, but the project itself is a cool idea and great implementation.