Brief technical analysis...
It looks as if Sikorsky have gone a long way towards minimising the hub drag normally associated with coaxial helicopters. The "flying saucer" hub shrouds will minimise drag across a small range of attitude trims, while reducing upwash losses. The pusher prop will provide forward thrust without the nose-down attitude normally required by conventionals, thereby minimising the range of attitude trims. Horizontal tail surface will likely help with speed stability. The ABC principle will also reduce power losses associated with retreating blades.
The pusher prop is assumed to be constantly connected. This configuration will offer advantages in height-speed energy conversion, or entry into autorotation. The extreme rearward position of the pusher prop may cause pitch/yaw coupling in fast manouvres. The square tip prop will allow high speed, but is likely to be noisy. Although a rear gearbox is not required, the long driveshaft will need to be of substantial design for the propulsion power.
Yaw control still appears to be by differential collective across the rotors. This will result in reduced yaw effectiveness in reduced g manouvres (hard pushovers) and autorotation. If the vertical tail fin is "ruddered" with the pedals, this will allow good control to maintained with forward speed. The inverted position is likely to be in order to maintain positive yaw control in autorotation.
They say a picture speaks a thousand words...
Mart