Best feature of this lens is clearly size. The camera almost looks naked. It's not the fastest - neither with focusing nor with the size of the aperture - but it does it's job. After all the praise, mainly on POTN, I was first a little disappointed. Especially compared with my Sigma 35mm/1.4 the picture quality is just not quite the same. Not as sharp and the blurred background isn't as pleasant. I used it primarily inside, with the aperture wide open. It might perform better outside with more light.
However, due to it's tiny size I tend to pack the camera more often. While the Sigma is kind of a beast that makes me consider bringing the camera twice - the little pancake requires no thought at all. Just throw it into the bag and off I go. It does start to grow on me.