So, lemme talk a bit about my experiences (without any spoilers of course!) from my time playing the game.
I've played about 5-6 hours and I just left the more restricted starting area (which is still pretty big and open) for the fully open world about an hour ago.
First of all, the visuals of Horizon are absolutely stunning, just as they promised. No stealth downgrades shortly before release for once. It's almost like experiencing a game on a new console generation for the first time, even though it is not a new console generation. It's similar to how GTAV felt when it first came out on PS3 and Xbox360. In size and pure detail is was way beyond all other open world games so far. The same thing applies to Horizon. It's basically Uncharted 4 visuals just on an open world scale. Just take a look at some of the screens that I already posted in the graphics thread:
http://www.freestepdodge.com/threads/the-art-style-and-graphics-discussion.5842/page-94
The story is really good and engaging so far. Compared to many other open world games, like The Witcher 3, Skyrim or Final Fantasy XV, the story is told tightly paced and you are effectively made familar with your main character and several others surrounding her. Early on I started caring for Aloy and her world and there are a lot of mysteries that you and Aloy want to unravel during the course of the game. Its really intriguing world and lore has definitely sparked my interest. I have the feeling there is much more to the game's story than what is visible on the surface right now. There are some hints in the game...and people, who have already played the game, suggest that.
Gameplay is great. It's very streamlined and if you want to be mean, you could say it shamelessly stole all the best mechanics from other games such as Far Cry, The Witcher, Uncharted and Zelda. It all blends very well together though, so who cares, right?
Hunting the robot dinosaurs and gathering their parts is really fun. Especially the bigger, stronger and more challenging they get. They are also quite clever and if you don't use your brain and plan anhead, they will annihilate you. Human foes, which you encounter way less regularly however, are not so clever so far.
Overall the game is pretty challenging...but there is also an easy mode if that is too much for you.
Side quests are fun too. There are no simple hunting or fetch quests or mindless mini games that are meant to pad the overall play time. There are fewer quests and activities as in other open world games, but all the quests and activities that are there are meaningful and rewarding.
Yeah, that's my early impression so far.
Can't wait to play more. I actually like it a good deal more than FFXV, when I was 5-6 hours in there.
