Critique of the device, or my idea?
My idea would involve mapping all the buttons to other functions, making it quite a bit more useful than "half a keyboard".
Well, the device. The problem is it isn't programmable. You can't remap the buttons without that affecting your main keyboard, making this board good for situational uses at best, such as Hofy's idea.
Now maybe it has full n-key rollover, making it an upgrade to most keyboards. But I wouldn't put money on it.