I have had a canon and Nikon copy of this lens, and both have been fantastic. A very usable range and nice fast constant f stop. Sharpness is good at 2.8 and great by 3.5-4.0 onward. I usually shoot my portraits with this lens around f4.0 and results are great. Colors and contrast are very nice for the cost of this lens. Build quality is decent, not pro quality, but overall good. This lens does like to suck in dust when zooming, so dusty environments I would go with a different lens. I currently have one HUGE spec of dust on the inner element that really bugs me, but does not affect pictures at all. AF is noisy, but fast and accurate for my needs. Filter does not rotate during zooming and focusing, so CPL filters are good with this lens. The included hood looks nice on this lens and does its job. Fairly resistant to flare and ghosting, but not the best with sun in the image.
Overall, I give this lens an 8 / 10 for the price / performance. Highly recommended.