Well most people I know how have this lens just use it. I can give you my short personal findings especially in comparison to the AF-S 400 E FL I used before.
Sharpness
One word: Outstanding! But that are all primes since the G-version. I used the 200-400/4, 500/4 G and E FL and the 400 E FL as mentioned.
With TCs the Z-version is a bit better but nothing you would find in the final image.
VR
That’s a big improvement and for my style of photography a huge benefit. I would say the VR is 1 to 1 1/3 stop better.
AF
In combination with the Z9 the AF is a bit faster and more accurate. Something else I observed is that the subject recognition is faster.
Handling
For me it is more or less perfect. I can easily use both controllrings and the front FN-buttons during hand holding the lens. I’m 199 cm so maybe this lens is designed for tall people.
The weight saving is great and the balance even better. The weight saving is even higher because the lens hood although is 130 g lighter and you don't need the FTZ adapter anymore. Most of the weight is now in the back. Not in the front and not in the center. For hand holding that is great. And I was already hand holding my old AF-S 400 E FL a lot.
Well and then the outstanding feature par excellence, the built-in converter. Like yesterday evening.
Sadly the bagder come out at the wrong side of the den. I needed the TC. Not the capture I was after.
ISO 5600, 1/250 sec, f/4, 560 mm
Suddenly a fox appeared. With a switch of a finger I was back at 400 mm. With an external TC I would have missed that shot.
ISO 7200, f/2.8, 1/80 sec, 400 mm
Because the capture looks a bit soft in this forum you find a sharper versin here.
So for me and the way I shot and what I shoot this lens is the best lens I could imaging.