FX D600/610, a good place to be.
My decision earlier this year in upgrading to a full frame sensor and thus the Nikon D600 was primarily influenced by the 24.3MP sensor in this camera. Considering signal-to-noise ratios, ISO, resolution, and the resolving power of available lenses, 24.3MP is in my opinion, the optimum sensor resolution for digital FX photography. The very same factors apply when the D600 is used in DX mode at 10.2MPs; the camera software can apply decent noise reduction to a photo at reasonably elevated ISOs.
In my initial research, it did not take long to establish, that the Nikon D600's 24.3MP sensor is a Sony-built IMX128, manufactured under Nikon’s specifications. Both the Sony FX a99 and Nikon’s FX D600 have the same sensor with probably some small different tweaks. It was no surprise, that the Nikon D610 will include this same 24.3MP sensor. The new Nikon Df DSLR Camera will incorporate the same FX 16.2MP sensor as the Nikon D4.
Over the last decade based on a 35mm film format, the CCD and CMOS sensors, both cropped and full frame have taken the industry from about 3.2MP to 36.3MP images, and now, we are starting back from the high to FX at 16.2MP; which signifies technological advancements over sensors produced just a few years ago. Rumors already suggest a D4X with the Sony 36.3MP sensor; further suggesting maybe not enough Pixels in the D4, or whatever. It may also suggest that some folks feel the D4 should have had the tried and proven 24.3MP sensor in the D600/610.
The oil and dirt issue on some D600s is what it is, and regardless, ownership of a Nikon FX 600/610 is a good place to be. The Sony a99 still sells for body only at $2800.00, and I bought a refurbished D600 for $1595. So far, I have had no issues with my Nikon D600.
I go along with the Industry hitting a brick wall on existing 35mm digital technology, and look forward to maybe a 70mm format camera, with new lenses to accommodate the larger format.