Unlike many purported "solutions" to typing problems, Half-QWERTY has actually been tested – at the University of Toronto Input Research Group (with which Matias is affiliated). After about ten hours of practice, most test subjects were typing with one hand at over 50% of their two-handed typing speeds; one subject hit 88% of her two-handed rate. Errors, however, were about twice as frequent as in two-handed typing.The post also mentions a few caveats, notably the problem that if you do not already touch type, usage might be a bit difficult to pick up. For touch-typists it would obviously make a great keyboard for mobile devices. For more on the idea of “one hand clapping”, you can look up Koan at Wikipedia.