Upload & Sell: On
this must be a lens by lens thing - my 24mm/f2.8 was essentially useless on the D7000, same the 50mm/f1.8 which just wasn't sharp, all across the image. On the D600, both lenses are much sharper. I read something about the "angle of the light" in another thread, which discusses how FX lenses are designed differently from DX due to the way the sensors respond to light at various angles. Seems like there's a lot going on and not all FX lenses work well on DX sensors, even if you just grab the sweet spot in the middle.
I will agree 100% about some lenses not being Dx friendly (one 50/1.8 I tried wasn't very sharp regardless of aperture/light/focus, my Series E 50/1.8 I think speaks for itself). The Series E 28/2.8 is super hard to use and only seems to work (to my standards, which admittedly are very lofty) in the lenses sweet spot of f/5.6. What kills me is that some Dx oriented lenses can suck too. The 18-105 kit lens that came with my D7000...I could not get a sharp shot out of it to save its life (its selling paid for my first fast 50/1.8D, a very sharp lens).
The other thing I will agree with 100% is the Dx viewfinder (in general). It leaves a lot to be desired. I wear glasses and this compounds the effect. It is exceedingly hard to focus sometimes. The Nikkor-Q 135/2.8 is a bear to focus through the viewfinder at anything faster than f/8. I have yet to take a shot at 2.8 using the viewfinder that was in focus...not a single shot. Luckily the Live View is good and I can then focus there. Requires either a steady hand or a tripod, but workable.