I have not used this device so my comments don't have too much weight. But from the look of the thing, the design doesn't seem to make for efficient use of the finger buttons. With the illustrated grip, it appears that only one top button is accessible to the index finger. Considering the shape, if might take some time to learn where the "hidden" grip buttons are, not to mention that attempting to trigger them will most likely move the mouse. And there is no scroll wheel. Personally, the thing looks painful to me both ergonomically and aesthetically.
