I'm not sure why people complain about build quality on this lens. Sure it's no L, but it is built more ruggedly and solidly than the EF-s lenses. It's solid and has a good feel.
The sharpness beats my 10-22mm, and in some cases can beat my 50mm f1.4 prime (though the prime wins for the range of it's optimal sharpness.) Contrast isn't as high as I've seen on other lenses in this range, but that's an easy tweak in post processing. Colours seem great so far. The hood is actually much more solid than my Canon EW-83E, but that may be due to the narrower body. I have no complaints, I only wish it were a bit quieter when focusing.