I am also experiencing extreme jitteryness. I tried to calibrate, and the blue circle shows up, but does not seem to move as I move the Leap. Or, it does move, but not in a way to coincide with my motion. Then, it will disappear and my score will go back down to zero and I have to start over.
I am following the directions, aiming the Leap at my monitor and holding it about 4 inches away.
The problem I am seeing is that even when my hand is perfectly still, the hand in the diagnostic tool is jittering around. It cannot seem to notice individual finger movements very well, and is somewhat laggy.