This game gets a solid 9 from me - the most solid 9 I'd ever give something.
I'm only 1/4th of the way in but I can't put it down. The world is gorgeous, the music is incredibly well orchestrated and positioned throughout the game, the combat is deceptively profound and the story of course is thrilling. I don't think I've played a game where fighting enemies is as fun as they are here. My mind's been blown several times already by the sheer scope and creativity on display, and I still have 75% of the game left to go through.
My only complaints so far relatively minor. Performance wise, the animations during cutscenes and scripted events seem to stutter quite a bit - enough to be noticeable. But what really bugs me is the lack of control mapping or sensitivity adjusting. During the more difficult battles, it takes a lot of button presses to do seemingly simple tasks like crafting and reloading, and then you factor in using traps and potions, you end up with a lot of accidental button presses. I've gotten used to it by now, but I'd remap some things if I could. I also wish we could detatch the camera from Aloy in photo mode.
I'm sure there are more stuff that might bother me later on, but overall I'm really enjoying this game. I'd have no reservations saying it is my favorite title because of how enthralling the gameplay is throughout. And when the world is this vast, the music is this beautiful, and the game is this polished, I imagine I'll be playing this for a very long time.