I LOVE this lens! It's wonderfully compact, solidly built, perfectly sharp and rich in contrast. I wouldn't mind if it was faster in low light, but not if it sacrificed image quality throughout. I think the design goals were excellent, as was the execution. If I had a problem it would be that I can't rotate my circular polarizer with the hood down like I can on some other Pentax lenses with the hood dropout that provides access to the filter. I have to retract the hood, rotate the filter until I get the effect I want, and then put the hood back in place. It only lasts a moment, but it's a moment that repeats itself ten to hundreds of times in a day of shooting. Time and frustration add up. But I can't bring myself to give it one star because the picture quality is just superb. :) Contrast is a key factor in my work. I often shoot into a light source. It's the only lens I own that handles this with ease and doesn't require extensive editing to bring lost contrast and shifted colors back to where they always should be. The fact that this is also an ultra wide-angle lens is a real bonus for my work. Wide enough to show a wide field of view, but not so wide that perspective distortions are distracting. Now all I have to do is find the perfect combination in a short telephoto lens.