According to our sources the Sony pancake is a 16mm f/2.8 lens. With a diameter of 49mm it has a bigger size compared to the Olympus 17mm f/2.8 Lens or Panasonic 20mm lens. The Lens comes in silver (not sure if it comes in black also) and compared to the Olympus or Panasonic MicroFourThirds lenses it has a superior build quality (chromium?).
According to the sources the image quality is very high and the price very low. In fact the NEX3camera + 16mm lens will be cheaper than the Olympus E-PL1 + kit lens.
Along with the pancake lenses two zooms will be launched. The 18-55mm and one more tele lens. Also this lenses do have the same high-build quality.