>> Agree - though that may not apply, with hindsight, to pro DX glass..
I think that is an intangible reason to go FX, in order to cement the utilitarian value of the lenses. It's why I never ended up with a 17-55DX. I bought the 24-70 FX because I knew that was my future and it hurt me badly until I got the D700, only because 24mm isn't wide enough for me, for that class zoom, on DX.
Normally I would not be excited to trade lenses for a body, as you did, but in your case you have what you really need, in a good range of focal lengths, in FX, so you basically traded lenses for a format change that agrees with you.
So I think it was a very productive trade and it will do far more than the incremental benefits you would get from trading the D300 for a hypothetical D400, for example, or doing some sort of lens upgrade in the same focal lengths you have.
I previously saw your comment in your first link, and that was why I added that quip about pulling the 85 once or twice a year .
I put my first Katz eye screen in my D200 and that worked out well. I put one in my later D300 but I was never fully happy with it. It did not quite seat right. But I had a larger problem with MF lenses...
The Katz eye screens do not and cannot spot meter correctly when the spot is in the split prism donut area. I assume that is why spot metering was never incorporated into any Nikon cameras with stock manual focus split prism screens (as far as I know). It was coincident with the F4 and N8008, with their plain AF oriented screens?
With an AF lens this was not an insurmountable problem for me, at least with the D300 and D200, because I would just move the active AF sensor to the side, outside the donut, and the spot would follow.
However, Nikon, it it's wisdom (which I seriously question- it's a bit nit with me), decided that with MF lenses the AE spot would NOT follow the active focus sensor, remaining "stuck" on the center sensor and center of the screen. Since my biggest need for manual focusing was with my MF lenses, and in particular my 500/4 Ai-P, I eventually removed the Katz eye screen. And since I typically shot the 500P at f/5.6 with a TC-14 the split prism did not work as well as it "should" with a properly fast lens like the 85/1.4.
You probably ran into this with your D300 and your MF lenses?
After I replaced the 500P with an older AFS version, and got the D700, I decided to remove the D300 Katz Eye and just not use that camera for manual focus except in situations where I could use LiveView, which is really the best way, for me, to go about that anyway.
When I got my D700 I revisited this issue, and had a very long phone conversation with Rachael Katz, discussing this entire issue of the viewfinders as they then exited on the various FX and DX cameras.
As a result of that discussion I decided not to attempt to install a Katz Eye in my D700, and for the most part I am happy with that decision because I don't have the related spot metering problems. I'm getting along well enough with the stock viewfinder, which I find far easier to focus than the stock D300 viewfinder.
I'm not sure if it was made fully clear in your 2nd link's discussion of this, but basically the accuracy of a viewfinder is proportional to the "grain" built into the viewfinder. And it was that way in the MF camera days too.
I still have special viewfinders for my OM1 that are intended for astrophotography. Those viewfinders try to solve the problem of not being able to see and focus typically very dim objects with very long focal ratio lenses on a standard ground glass screen (at up to f/40 and beyond with various negative lenses acting like very powerful TC's).
One of those screens is an "aerial image" screen, which is perfectly clear (no grain), with a pair of crosses. The image has a huge and artificial apparent DOF. Focus was achieved by moving the viewing eye back and forth, and focusing until the subject (always a bright star) stopped twitching between the cross hairs as the eye was moved. Not fun at all but that was how it had to be done. It was all done on the basis of parallax.
My understanding, based on a now somewhat dim recollection of our wide ranging discussion, is that the FX viewfinders are inherently "grainier" and darker than DX viewfinders, but they appear as bright, or brighter to some, than FX viewfinders. There is a complicated dance going on with the size of the viewfinder (proportional to the sensor size), the amount of light leaked to the AF and exposure sensors, and the resulting "look" when the light reaches our eye. That seriously favors FX and it may have some bearing on the compactness of the AF sensor cluster in the FX bodies (just my guess).
You might find it interesting to photograph a ruler with well contrasting ruler marks, at about a 45 degree angle, at a very close distance at or near minimum focus. Not to test the point of focus, but to test the visually perceived DOF in the viewfinder by estimating the range of ruler markings you can see with your eye and then comparing to an actual image. Do that at 1/3 stop aperture increments from wide open to about f/4. I suspect you will find that they correlate only at about f/2.5 or smaller.
For that reason I never considered an MF 85/1.4 and I try not to have to manually focus the 85 with even my D700 viewfinder (without a split prism). I knew from experience with my 50/1.2 that it would only be more difficult at a longer focal length. Even shooting the 50 wider than f/2 is a game of diminishing yields without using LiveView.
I did that ruler test with the D300 and D700 shortly after I got the D700. Partly to try to come to a decision about the Katz Eye. I don't recall the exact measurements I got but the D700 was noticeably more accurate in that way, but still far from perfect at f/1.4 or f/1.2.
I always thought LiveView was the best invention in the digital age, but it is not very helpful for most portraiture except maybe in a studio environment with the model sitting on a chair and the camera on a tripod. That's not my style. I'm not an advocate of EVF but maybe this is where it would be helpful?
I found the zoom option you are missing... custom f1 on the D300 and f2 on the D700 (Multi-Selector Center Button/Zoom On-Off). I forgot about that and probably have never used it.
That is a mighty fine ISO 25,600 image! I suspect that camera could easily go to 100K but Nikon basically feature crippled it? Probably high enough for most work and the camera might do ok with an intentional 1 stop underexposure to simulate ISO 50K?