So far so good. I'm not expecting $1500 L performance from it. But it's centre sharpness at f/2.8 makes it highly usable at that aperture. It kills my 24-70 f/2.8 at f/2.8 but that would not be hard. Corners can get a little mushy at f/2.8, but this is not an issue for most subjects I shoot. There is noticeable vignetting at f/2.8 but this is quickly fixable in LR4. Soon the fix will be automatic when LR4.x is released with updated lens profiles. I have an LR default set up for automatic lens correction on Import. Stopping down to f/4 ramps the IQ right up with f/5.6 delivering excellent results right across the frame.
Let's not forget the indisputable fun factor of such a tiny lens. And I just leave it on the body as a functional bodycap!
