The prototype is being developed in partnership with Fujitsu. As you can see, it is transparent to some degree, and it is an LCD screen. The screen measures 2.4" with a resolution of 320x240. Yes, that's tiny, but NTT is planning to develop a larger screen.
While it doesn't look like much, I'm rather interested in how you can manipulate it. We're all used to 2 fingered gestures, but this dual sided screen has that beat. Now you won't be limited to having only one fingertip on a particular point in the screen; just use the other side. You can even have the finger tips cross over each other as part of some complex maneuver. Even simple games benefit. In the following video, watch how the tech demonstrates how to manipulate a Rubik's Cube.