From one of the flickr Sony groups I belong to.

Not to excited about the APS-C... really hoping for a FF
but the Exmor R Sensor sounds cool...

Developed exclusively by Sony, this radically new design adopts a unique ‘back illuminated’ cell structure. The sensor has been re-engineered so photo-sensitive areas receive maximum illumination, unobscured by a grid of fine metal wires that partially blocks the pathway of incoming light in conventional designs.

Exmor R CMOS Sensor approximately 2x increase in sensitivity compared with conventional models. This ensures brilliant, low noise-images, even in low light. Now we must wait to see whether Sony can translate this back-illuminated design to DSLR CMOS sizes.