First, the good stuff: I used the 85mm f/1.8D this weekend in a shooting, and it's just the bomb, I love it. It performs well both wide open as well as at the typical beauty shot settings of f/8–f/11. Here's a 100% crop from the RAW file, no sharpening or retouching, from a shot at f/8:

Now for the boring stuff. Ok, so here's the 50mm comparison from this weekend:
- All 100% crops from the area left of the middle, as marked in the first post in this thread. For me, this is an "area of interest" :-), as I usually don't have my subject in the corners nor would it be in the exact center of the frame.
- The crop is not always the exact same frame, but the idea was to have the in-focus area in the middle of the crop horizontally.
- I tested the Sigma last week and only noticed today that I had medium resolution set for the test shots, so they are smaller. But I guess the differences are visible anyway.
- The other differences in size are due to small differences in distance between camera and the chart.

As one can see, the 1.8G does not deliver substantially better sharpness wide open. The Sigma seems to be the best here, no big news, but also not so substantially, that I think it makes a difference. The older 1.4D seems to be great, but then again, it's at 2.0 (doesn't stop at 1.8), at 1.4 it's also rather blurry:

So now, here are the crops from f/8. Looks like all lenses perform well, as expected, with the Sigma being the only one where I think I can spot a small disadvantage. With all lenses, there's a substantial focus shift when stopping down, which is why the crops from f/8 are all shifted, too.

Summary:
I'm a little disappointed from all lenses regarding their wide-open performance. I did a couple of test shots with people in low day light and they confirm the look that is displayed with the focus chart shots. No, I don't think it is asked too much if one wants good wide-open performance, the 35mm f/1.4 Nikon seems to be capable of delivering that, as does my 85mm f/1.8 at 1.8, most likely also the 1.4, didn't someone want to post test shot crops here?
Anyway, I now understand the market gap that Zeiss are trying to fill with their announced 55mm f/1.4 lens. Even if I had the 3k bucks that they apparently will want to price it at, I'd still not be into it due to the missing auto focus.
I think I'm gonna keep the 1.4G and send the other ones back:
- The 1.8G doesn't perform visibly better (to me), although what's really cool is that it weighs next to nothing, extremely nice! Anyway, I'd rather have the larger aperture than the smaller weight.
- The older 1.4D is the winner for its looks, as I said before, it looks small and old-school and a little stupid on a D800, which I personally love. What indeed IS stupid, though, is that it doesn't even come with a proper back cap, but a cheap slip-on cap that is just there for the packaging. Of course, there's also no hood included, and the one that one can buy is very short only. At f/1.4, the G is less blurry than the D.
- After all, the newer G lenses are also said to me much more dustproof than the D lenses, which does matter to me.
I know, there's a lot more to a lens then a focus test chart performance. :-) Anyway, this shows the sharpness rather close up. For real-world performance, not many of the other technical aspects really matter to me, except for coma and flare, maybe. Corner sharpness and falloff don't really matter to me on a 50mm, plus the latter can be easily corrected. Distortion is within an ok range for all of the lenses. The quality of the bokeh: yes, it's different, I'd say the 1.8G is the smoothest, 1.4G is almost as smooth and the old 1.4D is the most "nervous", which is what other people say, too. But to be honest, I don't think I'd notice the difference as much without a side-by-side comparison. I remember shots that I took years ago with the D700 and the 50 1.4D where I always thought the bokeh was very smooth and pleasant.
Anyways, maybe the overview helps someone on their decision in the future. Or coping with the shock when they notice how blurry their lens is wide open. :-)
Best regards,
Chris