Some month ago i had tested a Nikon Z9 and liked it, but even for me having a lot of large Sigma primes i found the body too heavy.
So it is a good thing Nikon came with a lighter version of the Z9 called the Z8. It lacks a few options of the z9 like GPS, but mostly it is a Z9-light.
The camera grip and weight is like the D850 - larger than a Z7 and more heavy. It has the same amount of pixels as the D850, but a very different sensor that builts the image in 1/270 of a second instead of 1/15s ( source Jim Kasson). Because of that Nikon decided to skip the mechanical shutter all together.
Coming from a d850 i must say it is a very different camera to use and I do not like to use them together for i get completely mixed up.
I have bought only one Z-mount lens ; the 40mm f2 lens - a small capable walkaround lens was missing and i really like 40mm and this one is very cheap and also better than expected good.
strong colors,( good coatings) , sharp enough, no color fringing - only some purple fringing...and very nice rendering and bokeh.
My other lenses are all F-mount that i use with the adapter and every thing work perfectly, even the Sigma primes.
The pure sensor quality at basis iso has a bit less dynamic range than the D850 and it has dedicated pixels for focussing, so all in all the D850 still has it place.
However with moving subjects the Z8 can make photos you never can make with a d850, its focus system is leaps ahead.
High iso is a bit more noisy than the d850, but the colours have more purity and produce beautiful images.
Not before it was so easy to get the shot sharp where you wanted it to be; even in dark circumstances it can lock on the eyes of moving persons.
what more is there to like:
very fast working camera. Because of 20fps focusstacking and bracketing is also much faster.
the possiblity of 1/32000 shutter speed and even preshoot (jpeg only) ( saw a picture of a bullet leaving a gun)
silent shooting at 20fps in raw with no shutter shock or electronic shutter distortion
less problems with banding shooting projection screens at events ( good flicker reduction)
a very good VR that enables 1/4s sharp images with 40mm
a very nice tilted monitor
many custom buttons to make the camera your own.( a puzzle, but rewarding)
many kinds of custom displays in the monitor/viewfinder with the possibility of a completely clear viewfinder.
Better accuracy in focus and exposure because it is now all happening per pixel.
a beautiful electronic viewfinder that can show the actual exposure ( or not) and the resulting colour
ethernet to send your photos out to the web
etc
Not to mention 8K video at 60fps in RAW - all inside the camera.
All in all a very different camera than the d850 and much new to learn.
What is missing for me:
I would like Nikon to built in a wireless remote function inside the camera...
pixelshift as Sony has but more perfect implemented.
The Z8 inspired me to buy a 55 inch 8K LG TV ( cheaper than i expected)
Now i can really see how my complete photos look on screen for the first time and since i have a large printer i can do both the same size.
Great for refection of what you are doing. Essential really.