Watching the initial viewpoints of the new Nikon Z9 has led to some controversy.
The first one is the small buffer, only 30 shots before the buffer fills in lossless compressed RAW. That video was from a reviewer who only had slow XQD card. Another reviewer who had a faster CFExpress card got 90 shots. So a big controversy was generated over nothing. Next year when the next gen CFExpress cards come out this will not be an issue for people who need that performance, but that seed has been sown in peoples mind and will hurt Nikon.
Some of these initial reviews have been big events organised by Nikon, the camera getting passed from reviewer to reviewer. One video I saw, the reviewer was getting a good hit rate for focus on birds in flight but it some times struggled to initial get focus. Towards the end of the video the reviewer mentions that the focus had been setup oddly, not on animal or auto, so later he reset it and now the camera was focusing and getting that initial lock straight away. Someone watching the first half of the video would get a very different impression of the focus abilities then someone who watched all the video.
Some of the better videos have been with Nikon Ambassadors, some who have had the camera for nearly three months and really gotten to grips with the features. The problem with videos from these people is can you believe them? They are chosen by Nikon and would not want to hurt the hand that feeds them so to speak.
I think with any camera its better to wait until everything is finalised on the camera (these were pre-production models with early firmware), and a reviewer that can spend some time learning the ins and outs of the camera. The release of the Z9 by Nikon has been handled fairly well, much better then the Z6 an Z7 which had very early firmware and still were not focusing very well, this was fixed and then revolutionised with firmware v2 and v3.