I haven't had a chance to test this on wildlife yet and in fact I haven't been shooting much wildlife lately, largely due to the seasonality (I'm looking forward to at least slightly warmer weather) but something very... confusing that I've noticed with my shooting of people:
I got my Z8 early this past spring and thought it worked pretty well. In mid summer I got the 70-180 Z lens - my first native Z lens - and thought that with the Z8 the AF was amazingly accurate and the lens to be the sharpest I'd ever used. By November, I was feeling a bit less happy with the AF and was finding it very inconsistent (on both the 70-180 and another lens of mine), especially in lower light. I also noticed a weird AF behavior in that using the wide area AF modes with subject detection tended to give me low accuracy for AF on people's eyes - it would say they were in focus but they'd be extremely soft or often just plain out of focus - but if I used the full area AF the eyes would be in focus much more consistently. It was still far too low, but it was better. With wide area modes I'd get <50% in focus when the eye box was solid green. With the full area I'd get 70% or so in focus with the eye box solid green. Meanwhile, doing it with the single point AF and no subject detection was >90% in focus.
Then, as the winter wore on I started to find photos from my Z8 to be weirdly lacking in sharpness and also increasingly noisy/grainy in a way that even LR's denoise wouldn't clean up. This really confused me because I was taking photos at lower ISOs in better lighting with less noise (or grain; it was hard for me to classify which) than I'd seen in lots of past photos but the past photos would clean up to near perfection in LR's denoise while anything I was taking now come out of denoise looking hardly any better than they went in. I was seriously starting to consider switching brands, even as a bit of a Nikon loyalist, because it all started to make some of the stereotypical anti-Nikon complaints seem pretty real to me.
When the 2.0 firmware was released earlier this week, I first backed up my settings and then updated the firmware. I then restored my settings and verified that they did go back the way I had them - so nothing has changed in terms of how the camera is configured.
However, almost immediately I started to notice the AF being more accurate and the photos having that nice "high-fidelity" look I would have expected and had been used to when I first got this camera/lens combo. I didn't say anything at first because I wanted to test it more. I still wouldn't say I've tested enough to be certain anything's really changed, but in what playing around I have done it really does feel like a different camera, like suddenly the AF is nailing things the way it did when I first got it and like the photos have an appropriate amount of noise and that noise can be cleaned up in processing again. I can now go into whatever mode I want and photograph my kids, for instance, and their eyes are sharp and shiny almost every time. I can see the texture in their skin instead of a kind of very vaguely "oil painting" sort of lower texture.
This has me pretty confused because I am positive nothing has changed settings-wise and because I know that while this firmware is an improvement it isn't as if the previous firmware was so bad as that there should be this difference. I saw earlier today how Thom Hogan had pointed out that apparently the previous firmware wasn't always accounting for AF-fine tuning properly so I went and checked to see if maybe I'd had that turned on before and so now it was just being applied correctly, but no, it wasn't - and it certainly wasn't on when I first was getting great results last summer, either.
Just something to think about. It really makes me wonder what the heck changed, what the update fixed and how it fixed it, and how to make sure it doesn't happen again!