I did notice a big stutter exactly one time where the screen actually tore - I couldn't capture it and I was unable to replicate. I just assumed it was something in the background that caused it since clearly the game uses v-sync. A strange thing but super rare (at least here).
OK, there's one thing about this game that really caught me - the scale.
We have a LOT of open world games today, obviously, but I feel that many of them don't really capitalize on scale.
The Witcher 3 does indeed sport a large, open environment and it often throws massive views at the player but there's something about the way it is presented that feels off. It never really FEELS as big as it should. Does that make sense?
Conversely, this is something I feel that FROM Software nails with the Souls games even though they are not open world. The art and construction of the world simply conveys something massive.
I feel like Horizon actually does something similar. The environments just feel huge at times in a way that is very compelling.