Poor optical

I bought it with my NEX5 there are 1 year and a half. As soon as the Sigma 19mm 2.8 is out, I sold the pancake ...
Cause? No dive, even at F8. Its compact size allows it to carry everywhere, that's great. But when you look at his pictures on a big screen, one realizes the lack of sharpness, a blur below F8.
In short, unless you touch it used a third of the price, or not to be very little demand on quality, I advise to go your way. There is a Sony 20mm 2.8 which seems promising on paper. More expensive, but also compact.