Rationale: key-to-note assignment can be made symmetrical, so one can transfer skills between hands, halving the number of fingerings to learn.

Further:

• Each keyboard assignable to a unique instrument

• Each keyboard assignable to overlap the other to a variable degree, making "special" effects like contrapuntal motion simpler, even trivial

• One's hands won't run into each other

• Ends the tyranny of the right-handed keyboard on the left-handed

That's the Theory, anyway. What it the actual practice?

It works, better than hoped for (I had wildly hoped for 30%). The Actuality:

• There seems to be at least a 50% reduction in learning time for the left hand

• An unexpected (but obvious in hindsight) thing that happens is clumsiness transfer from the untrained hand to the trained hand. There are techniques for reducing this.

• I suspect some serendipitous (unexpected good fortune) benefits as well ... to be detailed.