9 out of 10 points and recommendedAffordable, decent construction, extremely sharpBarrel distortion and vignetting, not weather proof.
Other posts complain of distortion, low contrast, etc. The review points out that it has barrel distortion but it is easily corrected in Adobe Photoshop using the Warp function. As for low contrast, perhaps wide open but perfectly acceptable at F4 or higher, and you can easily add contrast with any photo software.reviewed March 30th, 2014 (purchased for $360)
I previously owned the Canon L series 17-40 and 16-35 lenses. This lens is easily sharper than either of those at any F stop, regardless of what others may say.
If you have trouble manual focusing then this may not be the lens for you because the deep depth of field even at 2.8 may make it difficult. But after you do some tests and learn where to set the focus ring it all falls into place.
As for the-digital-picture.com and Ken Rockwell being the only two accurate reviews of this lens, that is pure BS. DXOMark and Photozone.DE have both highly rated this lens. If one can't work around the known weaknesses of this lens, then get another hobby because you certainly aren't a professional.
A highly recommended lens.