Here's a press release on the ARG...
http://www.yachtforums.com/forums/ne...light=arg+gyro
It's not a new technology, but a new application of the same. It's a mechanical gyro that for all practical purposes, should produce better "static" results than traditional fin stabilizers, i.e. at anchor or docked.
As for anti-roll properties underway, I'm sure it adds a level of stabilization, however I don't believe it would be as effective as active fin stabilization, especially as speed or wave height increases.
The combination of both systems would produce the best results, however this would be expensive and would add additional weight. The added weight of the ARG is not be a bad thing, as this can improve stability at speed or at rest, given it's low CG placement within the hull.
The real upside to the Mitsubishi ARG is simplicity, as this removes hydraulics, plumbing or servo motors from the equation. It also means nothing is protruding from the hull, which decreases drag and eliminates the possibility of damage due to protruding fins.