I'm at around 23 hours or so, 35% completion mark. I'd give it a 7.5 so far, still pretty early in. As I do in all games of this type, I've been ignoring the main quest line as much as possible and exploring and finding side quests and stuff. In Fallout I got to almost 100 hours of play time without ever really progressing the main quest line past joining the Minute Men, which is like.. an hour into the game. In Skyrim I got well over 100 hours before doing most of the main quest line. Witcher 3 I have 40 hours or so and barely touched the main quest. The main issue I am finding here is that the side content in Horizon is nothing but filler. It's billed and talked about as an RPG, and in these open world RPG's you can always find killer side quests some of which rival the main quest line in terms of size and quality. In Horizon they all seem to be fetch quests, or travel all the way over here and track someone down in Batman detective mode. But maybe they get better, idk. I've read there are not many side quests though.
The one thing I have found that is entertaining are the Hunters Lodge challenges, mostly because they introduce some much needed strategy and thinking into the combat, where otherwise you rarely if ever seem to need it, even on the hardest setting. There was a challenge on one where you have to shoot the cannons off one enemy and use those cannons to kill two different enemies. It was challenging thanks to all three of those enemies having an instakill attack that could hit you at any time, and for the first time in over 20 hours in the game I found myself using the terrain to my advantage in combat, sneaking off into a small cave within the hunter area where the two smaller enemies I needed to kill were able to follow, but not the giant enemy. It's been very fun getting the max reward on these, even if some of them were also too easy. They reward massive XP, too.
The lore is great though and the detail in some areas are just amazing. I'll probably tackle some more of the main story today to progress a bit further.