Any chance you could compare it to the Z-mount Voigtlander 28 f/1.5 Nokton? To me anyway, it is an interesting question whether the Leica M mount 28 APO will outperform the native Z mount 28 f/1.5 lens on a Nikon camera.
Unfortunately I don't have a z mount 1.5 version. I did have the m mount version at one time and loved it. K actually regret selling it. But I can tell you the apo is definitely sharper. But the 1.5 is close behind.
I will say, I had the painted version and I thought it was the series and best built voigtlander ever.