The Sigma 17-70mm is the sharpest lens I have ever used. It has good macro capability and fast focusing speed among, I simply love this lens!
Most of my photos are taken in RAW format, then I use Canon Digital Photo Professional (DPP) to post process the photos. For the RAW files, I adjust brightness, set saturation to 1 or 2, set the sharpness to 4~6 for portrait or 6~10 for landscape, resize them to 30%, then upload. It doesn't take too much time.
I hope you love the Sigma 17-70 as much as I do :-)