Sigma art are the best lenses out there. This 50mm lens is much sharper than the Nikon 50mm 1.4g. I wish the 85mm ones were the same price as this. I used his 35mm and 85mm art lens on my d600 I purchased recently and photos were superb.
Never read that ,I know when reviewed by the Nikon magazine it scored best on test and highly recommended I’ve not had any problems with mine
Just bought the 150 -600 sport and this is also superb quality these lenses unlike most Nikon and others are made in Japan not Korea or Taiwan that should tell you something about quality
And sigma is still a 3rd party lens so can have some minor compatibility issue even though they have improved over the years