So, I'll add my two cents here, although I doubt I'll be able to add anything that hasn't been told before.
Being 1st person instead of 3rd person is not going to be a dealbreaker for me. I'm not going to pass on a good game just because I would have prefered 3rd person, but it's going to be detrimental to my enjoyment for sure. People tend to bring up games like Elder Scrolls or Deus Ex. Those are great games indeed, and I like them. But there wasn't a single play session of Oblivion or Deux Ex when I didn't think, "Jaysus this would be so great if it had been designed for 3rd person perspective". And I know that Oblivion could be played in 3rd person, but it clearly wasn't designed for it.
We all have our reasons, but for me, playing in 1st person has always felt like seeing the world through a window on the wall. It just feels constrained, limited, and if I increase the field of view (if the option is even there to begin with) to a point where it starts to feel less tight, then you get those awful curved edges and motion sickness kicks in.
I just don't like it. It feels weird and it feels unnatural, because even though it tries to mimic how we see the real world with our own eyes, the truth is that our own eyes give us a perspective and a peripheral vision that a 1st person camera in a videogame doesn't really mimic well, and the end result is a sort of uncanny valley where it's supposed to feel natural, but it doesn't quite manage it. It's actually one of the reasons why I've never been into 1st person shooters. It's not because of the sooting, it's because of the 1st person view.
I can see how this is going to be deeply divisive, because it's a matter of taste, of how different people experience the game. But personally, I can say loud and clear that it is a big disappointment.