I think Nikon created a hit but I did find a couple things surprising.
As someone who has shot Nikon since the F5 and recently moved to Sony a1 system this year here are my takes.
I like the built in grip, the Z9 is a sexy camera for sure! I don't mind the add on grip of the a1 and not having a grip could have some advantages at times but I have never taken the grip off so for me Nikon made the better choice with larger battery and ergonomics I suspect will be amazing. Win Nikon
I love that Nikon kept the buttons that light up! I miss this with the a1 as I do a lot of astro work. Win Nikon
I love what Nikon did with the sensor protector and how fast it appears to turn on and off. Sony uses an actual shutter to close, it works, it is slow and I worry I might damage the shutter which will lead to a costly repair. I will give this design a win to Nikon
I like the extra diversity of the rear screen on the Z9. I do prefer the rear screen to stay behind the camera as I am not taking selfies or blogging. I would say this is mostly a push between Z9 and a1 but would give the slight nod to Nikon for the extra tilt function. Slight win Nikon
Dual CF Express B cards. I haven't had any issues with the CF Express A cards (I have 3 of them), they are expensive, now with ProGrade they have come down a little in price but very limited choices. Speed of the A have been fine but I would have preferred B cards for the extra speed, especially in downloading to the computer. However Sony design does offer the best of both worlds with dual slots that support both CFA and SD cards. Much better solution then what Canon did on R3 with 2 different slots and what Nikon has done with cameras such as D850. I have never liked having 2 different card formats in the same camera. I give this win by a hair to Sony for 2 card types in one slot but still would prefer B cards like the Z9 (part of this comes from I already had B cards and readers I had to sell and replace when I went to Sony).
FPS: Well this is a bit confusing and unknown just yet. From what I am seeing I think Sony is winning this for RAW shooters. For Jpeg shooters it is a push except for the 120FPS reduced MP files. I don't see me ever using this for my type of work but hey why not include it if you can, even if there is very very limited real world use by the masses. For now win Sony
AF: To early to know, from what it looks like I am guessing Sony is likely still ahead but the gap has sure closed. Win Sony for now but way to go Nikon!
Lenses: Native glass win Sony
Lenses part 2: Adaptable glass and diversity especially with tilt shift and super tele win Nikon
Flash Sync: Win Sony
The Z9 doesn't make me regret leaving, nor would it make me come back however Nikon is on the right track so that is great! I suspect for many the Z9 keeps them for leaving which is also great! We all want and need Nikon to survive and thrive and I see the Z9 as the first real step in that future. Now if Nikon comes out with a PF big boy lens like is now rumored I sure could see buying that single lens and a Z9 or its replacement (not knowing when you could even get one of the new lenses (took me years to get a 500PF)) and using it along side my Sony gear.
I can't wait to see Steve get some seat time with the Z9 and report on what he thinks.
Today is a history making moment for Nikon as it has killed the DSLR, I see no reason to not invest into this new future.