With the NEX-C3, we saw a major improvement to this fault and it appears with the NEX-5N it at least didn’t get worse. I’m reading early reports that the JPG output is looking great with the corners exhibiting almost no weaknesses than the usual one would see with a wide angle. RAW output however still seems to exhibit some weakness but again at least better than the last generation.
Below is a picture taken with the 16mm F2.8 Sony lens. Not a great picture to show corner strength but perhaps a reminder that in many very wide angle shots, usually the corners don’t matter quite as much if you have a strong subject. AUTOHDR was used in JPG mode.