I never could understand how anyone would use a 3D desktop efficiently. The user can't really move through the space. The mouse or whatever you would use currently does not have a depth function. I don't like wading through files in 2D, let alone 3D. I've done a lot of reading and none of it seems to be in 3D. As it turns out, that's what matters. The way in which I learn and do work is an abstracted 2D technology (fonts, silly). Until the alphabet takes the next step to 3D, I doubt you'll see really efficient 3D desktops. I'm not saying it won't happen, I saying I have no clue how it would work.
I'd really like to use a big 3' by 4' 2D desktop with handwriting recondition software. I would be awesome to annotate class notes, do scratch work wherever, and not lose character sheets. Yeah, you'd be sitting at a table, but don't worry. There's a tablet that you can drag your work off of or on to it.
A little OT, I've seen print in the fourth dimension i.e. scrolling signs, but never really in the third. Who gives a shit if letters have depth?