The chorded keyboard is not as efficient as two handed QWERTY. Englebart reported getting 35 words per minute with his right hand and 25 WPM on the left after extensive training[1].
Granted, this is a good speed for having one hand free to use another type of input (pen, mouse, touch screen or whatever).
A chorded keyboard is also a promising idea for mobile computing where a dedicated physical qwerty keyboard is unwieldy.
I wasn't able to see enough of a benefit to try building one or purchasing some of the existing products. At the right price point, I definitely would try it as a novelty.
It seems there is a chicken and egg problem of inputs and software that makes you efficient using them.