I just asked you in another thread about the lens and only now I saw you created a special thread for the sigma. Ver fine results. Did you post processing? If so, what?
The images were shot in RAW and using a 580EX (-2/3 and -1/3) for fill light. Post processing was done in Lightroom 5, with a touch of exposure adjustment, a little bit of shadow and highlight work, curve adjustment and a pinch of sharpening.
The most challenging aspect was the balance of light between the dark inside of the aircraft and the bright outside area. The post processing work was mainly to adjust for this rather than any lens deficiencies. It may not be the sharpest tool in the shed, but you can sure cut your fingers on it
The top shot was used as article opening spread in one of the magazines I shoot for - the image was sharp enough that you could read all the dials and gauges on the glossy paper. Having said that, print is much more forgiving than pixel peeping on your monitor but I wouldn't use the 12-24mm for very large reproductions.
I just start to discover Lightroom 5. I usually use DxO Optics Elite.
I guess you are right about the pixel peeping. You see it more on the monitor rather than on paper. But I am not a pro. I envy you for such adventures so keep them posting.