I've left Nikon, but I strongly recommended getting on the wait list for one to a friend who is trying to find a single lens for her Z7 that will allow her to shoot wildlife and also other stuff on a 4 mile roundtrip beach walk to shoot an eagle's nest in FL. The 5.6 aperture at the long end means that she'll have a 200-800mm f9-11 with a 2x converter. I've shot my R5 and 100-500mm with both a 1.4x and 2x TC and have been able to achieve focus and usable images at the long end with each, even at f14. I've also shot with the 800mm f11 and had more issues with the image quality (which honestly isn't horrible) than I did with the minimum aperture.
I personally think it falls short of the Canon and Sony offerings, and given that the 200-600mm on the roadmap isn't an S-line lens it won't entice someone who's looking at all three systems trying to decide which one to move to for wildlife. But for folks who have already made up there minds I expect it to be a worthy entry in the mirrorless ultra-zoom race.
And not for nothing, but it's close-focus capabilities are about the same as my 100-500mm, and I can't tell you how much fun I have shooting "pseudo-macro" stuff when there's nothing else to shoot.