NEX 16mm and DXO Optics
Interesting question, that I would like to be answered too. What I can say is, that as long as you shoot jpg, the camera compensate for distortion (well enough) and most of color aberrations too. DxO can also correct color on a jpg image to some extent, and that is quite unique. Better if you shoot raw. I have done that (with DxO) on some pictures (jpg) taken with a Nikon P300, that under certain circumstances produces a lot of purple fringes. But I do not own the program.
I have the 16 mm F/2.8 lens and also the ultra-wide adapter. These make a cheap 12 mm lens. I have not used this 12 mm setup yet, but it will be within 1-2 weeks (inside some churches).