The weaknesses are to dominate

Wide for Sony APS-C camera. Sony, Tamron, Tokina and Sigma offer several wide-angle zoom. My purchase decision was determined by relevant comparisons. The last time I was undecided between the Sigma EX 10-20mm F / 4-5.6 and 3.5 zoom. The merits and demerits of the Sigma 10-20 4-5.6 I after its purchase exactly found as described elsewhere, but without any defects of the series dispersion. Hardly avoidable weaknesses of WW lenses are just distortion, vignetting and edge blurring that 10-20 F4-5.6 seem to me to best be addressed at the Sigma Zoom EX. If the weaknesses you fades in scene select something, for example, has little structure in the corners, then succeed excellent recordings. Distortion is at 10mm barrel-shaped, from 12mm cushion-shaped, at ~ 11mm in transition (see Ziegelwand examples), little CA, blurring only in the corners. Weakness is the vignetting, the strikes in the entire zoom range (brick wall examples). This effect, however, is easy to correct on the computer. Now even concretely:
+ The focus is generally very good to excellent, just in the corners it is moderately (by stopping down well).
+ The Verzeichung is almost not to notice, but in the corners significantly (10-12mm Focal Length.).
+ The lens is at a low focal lengths of light strong enough for indoor shots (without flash).
+ With a common 77mm filter size is used.
+ AF or MF are not a problem because of the large range of depth of field.
- For Sony no HSM and no AF / MF switch on the lens, AF camera with motor.
+ The lens makes a good external impression (mechanics, surfaces).
- The lens supplied via Amazon Marketplace is not available through Sigma-Germany, so the point deduction.
As the focus of use is for me at low focal lengths, I have dispensed with the F3.5 variant. This brings benefits only to 20mm down. Whether you want to have the 8mm recently offered Sigma 8-16mm zoom, everyone must decide for themselves. The 8-16mm lens has no advantages, rather slight drawbacks and also no filter use, no lens protection, higher price in the range 10-16mm.