This is my first weekend with this lens. Well, lots of good things to say about this little gem: sharpness is insane (with K100D), colors are great and build quality... well, it's a Limited!
Vignetting, CA and distortion are very well contained. Minimum focusing distance makes it great for close-ups.
I was first concerned by the AF accuracy and thought that it wasn't as good as the DA 40mm or even the kit lens... But this was due to the fact that the AF sensors in the K100D are way bigger than the little red confirmation square that you can see in the viewfinder.