Croft-an-Righ is dreadful.
Another cobbled street sports both some of the worst, and I think the best cobbles in Edinburgh: Cambridge Street. The section from the Lyceum theatre to Grindlay Street is bone-shakingly, filling-looseningly, wrist-fracturingly poor. However the new flat cobbles that go around the Usher Hall and past the Traverse down to Castle Street are wonderfully smooth.
So it can be done right, given the correct materials and the will to do so.