No two ways about it, this is an extraordinary lens. Its performance is superb, it is far lighter than it could be expected to be, it has weather sealing and the price is realistic. An ideal travel companion, with the bonus of that fast, bright f/2.8 aperture.
Outstanding sharpness, Low distortion at mid focal lengths, Low flare, Well-controlled CA, Virtually silent, fast AF, Light, Weather sealing, Matches 17-70mm, Modest vignetting