Generally Sigma lenses are good quality and work well, I have heard of some issues with the longer telephotos (70-200mm F2.8 & 120-400mm) and sharpness / focusing issues. I have owned both of these lenses but have never had any issues with them (Pentax and Canon mount)

I am at the moment looking at a Sigma 105mm f/2.8 EX DG Macro lens and wanted to know if they have the same quality control issues that the longer Sigma lenses have?

Paul