> This one's for those of you who've expressed interest in or are working
> with 3-D sound.
> I'm curious to know what you use it for.

Can't you imagine what it is useful for ??  
I'll do it for you (i have *too* much imagination ;-))..
Imagine a pale layer of meadowsounds beneath you while 
abstract cylindrical shaped textures float and fly above you
performing a vulometric choreographic ballad in the sky. 
You slowly start flying upwards and joining the turbulent 
dance of the textures. 

That's 3D-sound at its best.  

David.