When dpreview released the news about the new Nikon mirrorless people all over the world were complaining about slow load times on the website there was so much interest. Of course when the first comments are made on a new release from anyone it always seems to be a race to see who can say the most negative things about it. They look like really nice cameras and may be perfect for some depending on what they intend to do with them, and of course they will always be tweaking and adding new changes in future - perhaps the Z6S and Z7s will have twin card slots - they have to give people an incentive to upgrade in future. Some may use them for the video features and not care about any of the complaints about the stills side of it. Others may be perfectly happy with the stills frame rate and not care about video.
But: The biggest issue I can see is only one card slot. Even though the xqd cards are supposedly more reliable than SD cards, and faster, no card is perfect. You wouldn't want a card to fail during a really important shoot with no backup. I would rather have my D7200 with twin card slots than one of these bodies at a wedding. Also the rated 330 shots per battery charge is dismal. My old D5200 has a rating of 500 shots per charge and mine always seems to run out much too soon. There are always many variables involved and most likely if you spend a lot of time going through menus and watching the screen when you don't need to you could get less than 330 shots, but if you are shooting at a fast frame rate and not doing a lot of chimping I imagine you could get 2000 shots on a battery charge.
At the moment I will do what I normally do, sit back and watch the scramble for the 'latest and greatest' and maybe in 5 or 6 years time buy one for $800 when they are considered "not up to scratch" any more, which is what happens with digital gear. I imagine by then though a dx version will come out - unless it has twin card slots like my D7200 I won't be getting one. I'm hoping that they take the D7500 sensor and produce a dx mirrorless that does 20 fps stills and some high frame rate video. The J1 could do 1200 fps, I think they can do better than that with a lower res sensor than the Z7 [the Z6 does faster frame rates because of the lower megapixel count].
Either way it will be interesting to see where this goes, it's good to see competition between the companies, us consumers are the ones who benefit from it.