I've been playing with it a bit, and think the following would make it a bit better:
- Moving between asset folders/groups is a bit clunky - maybe have tabs or a drop down list, rather than having to cycle through them?
- The actions at the top (new, save etc.) look like menus but they're actually buttons. Maybe make them look more like buttons, or have normal menus?
- Being able to position some simple directional lights in the editor just to get a feeling for the scene would be nice.