Is this product strictly for people missing a hand? I can’t see any other market. Sure it looks and feels cooler to type with one hand, but that is not nearly enough benefit to cut your typing speed in half.
I, personally, would find this useful for doing work with a photo editor, 3D modelling tool, or some other program where I would otherwise be rapidly switching between keyboard and mouse.
In terms of raw typing speed, I don't think that it can ever come close to the performance of someone using a machine-optimized keyboard layout with two hands, but I very much like the idea of not needing my right hand to dance back and forth between the mouse and the right side of my keyboard.
I could see myself using this in Lightroom where most features can be triggered by a keyboard shortcut but then manipulated (i.e. dragging sliders) with the mouse. It would be faster to have one hand on a full keyboard and the other on my mouse, rather than moving my mouse hand back and forth or using the mouse to invoke all the features.
In terms of raw typing speed, I don't think that it can ever come close to the performance of someone using a machine-optimized keyboard layout with two hands, but I very much like the idea of not needing my right hand to dance back and forth between the mouse and the right side of my keyboard.