Dave,
Yes, I thought that a slow rotor might be the case! Not sure where it can be seen that the retreating blade has a negative pitch though, perhaps because the picture you have posted is not detailed enough. Has the designer come up with a new idea for radically adjusting the inputs on the retreating blade to give the required negative / reverse angle of attack?
I think it's probably true to say that it has been tried before. "BERP" Blades, "Advancing Blade Concept", "Convertiplane", blade rigidity / stability problems at low Nr and high forward speed, "X-wing", blown blade surfaces, plumbers nightmare, etc etc.
And then of course, in the not-too-distant past, the larger manufacturers filed it in the all too difficult drawer and designed the tilt-rotor as a possible alternative. As we know, that has it's own problems too, some of which make it not such a good alternative to the conventional (but slow) helicopter because of handling / manoeuvrability problems in certain flight regimes, as was tragically demonstrated on at least two occasions not too long ago.
Sorry to sound sceptical but I am so! If it works though it would be a great thing.
What say you, Nick?