I'm 6-7 hours in-game. As for now, it's a mixed bag at best. Walking around, hiking on the mountains feels great, same goes with asynchronous multiplayer. The thing is, game do not let me enjoy it, throws BT's in every mission at you, encounters with them quickly become an annoyance. In my current mission I have to get over the hill, which is flooded with them, and there's no way to avoid them. Open world feels very corridor'y, like Afghanistan in The Phantom Pain. Odarek (radar) lets me detect them, but it also puts markers on every single object in-screen, which makes hard to spot them.

In terms of the story... i don't even know where to begin with. It's all over the place, almost all characters are just an exposition dumps, like Code Talker in The Phantom Pain - Die-Hardman, Mama, Heartman, Deadman. I don't know anything about them at all, about their personalities, backstory. I don't care about them, same goes with Sam which is just a blue-collar worker, yet he's refereed to as a "legend". And it's laughable how many times you're being shown that Sam has phobia of being touched. I know MGS series wasn't known for being subtle (quite the opossite!) but this is just... embarrassing for someone being referred to as "master-storyteller".

First three hours have a horrible pace, most cutscenes from the trailers are thrown at you, one after the other, and there's minimal amount of gameplay.

I fully expect to get downvoted for my comment, but it's the worst written game by Kojima, characters talk all the time but there's no substance in the lines. As a someone who loves MGS2 and MGS3, I'm now fully convinced that he heavily relies on other writers, that's why quality of it is so random in his games.