Video and ultra-ISO are great, but the single thing which really annoys me about the D3 is how hard it is to shoot in manual focus. The focusing screens on autofocus cameras are generally not well adapted for the tasks that old-fashioned matte and split field screens were designed for. I haven't been able to reference this anywhere, but there is something different about the D4 focusing screen. You can just about see it in some circumstances where it appears to be ridged in some way. But the result is that it is much, much easier to focus the near-impossible Nikon 500 mm reflex mirror lens. Shooting with the D4, I was able to quickly and accurately focus on moving objects and fleeting images, capturing far more than I ever could before. If you rely on manual focusing with difficult lenses, this is probably enough to sell you the D4 on its own.
