This is my pal's view, I've not used an FX myself but we have chatted at length about it both before and after he 'invested' in the change
Most of the time his images are printed up to, but no bigger than, A3 in a Wedding Album and at that size then no, he doesn't think there's any real difference in quality to make the change worth it. He changed from a 24mp camera to a 24mp camera and, most of the time, he's shooting at lower than 1000 ISO and there's b****r all quality difference that he can see printed. So while he's happy with the D750 and the new shallower DoF at the same aperture, he doesn't feel the change was truly justified
So no, not a joke
Dave