in my experienceThe 3DOSX user experience is actually pretty good in terms of navigating the space, and always knowing where you are (in relation to everything else). Revealing that frame of reference is one of things that GUI professionals should always be striving to do and that present WIMP interfaces could improve upon. Forgiving its performance problems (one frame per second), 3DOSX is a far cry from the speed at which I can rifle thru WIMP based file directories, but is still a pretty good advance on a demonstration 3D interface from Microsoft. They represent the file tree as a hallway where you move forward and back to pick up files off of virtual easels. The files have thumbnail previews that help you understand what's inside. But while watching the demo video, I can't help but not know where I am in any sort of file hierarchy.
So, having a sense of spacial relationships between files would be a good advance, but here's a few problems that need to be overcome...