That is very, very cool. (Found my way here from "MAKE: Blog".) Clever idea for creating a 3D display system, I must say I'm impressed.

Looking forward to seeing what it will look like when you iron out the kinks in the programming. The disco effects are nice too, though.

Also, a question: did you ever consider using something like a rim drive type system to drive the the PCB rotation? Such as mounting them on e.g. a thin aluminum disc that is then suspended in the center (possibly "in between" the two twin PCBs), balanced, and then driven along the circumference (either by having the aluminum disc acting like a gear wheel or something else). (I guess pie-in-the-sky would be something like Sbarro's hubless wheels, except adapted to this problem.)

Of course, it'd be a vastly more finicky and problematic drive/mounting system, especially for undertaking as a first technology demonstrator. The main advantage would probably be a lower center of gravity for the system rotating along the vertical axis and potentially nothing obscuring the view (just in case you do get to mount a couple of OLED screens on there).

Anyway, just some thoughts. Again, very very cool. Nice work!