Nokia has some good information in a whitepaper -- see link in one of the many other 808 threads. The short story seems to be that there is no big problem putting standard phone-camera sized 1.4 micron pixels on a far bigger 1/1.2" sensor -- the challenge is processing speed, like handling over a billion pixels per second in video mode. For that, Nokia had to wait for processing speed (and its partner Toshiba) to deliver a custom chip that handles the downsampling before the signal goes on to the usual image processing chip.
Then again, I have been saying for years that it is mainly processing speed limits, and the need for adequately high frame rates, that has been the main limit on pixel counts, not per pixel technical data like engineering dynamic range. This sensor will put that idea to an extreme test, when compared to 10mp premium compact cameras like the Panasonic lx5 or Canon G12, which have far bigger photosites but distinctly smaller sensors.
