I was always able to play above ~40 in the worst places without issues, most times around or above 60;
I returned to using normal crops recently, tho (I was using Amber's simple crops) and in huge farms I go down to 20~30. Even smaller farms cause stuttering - no fps drop, but stutters - when moving and new parts of the world with lots of things (like crops) are loaded. There seems to be a lot of visual artifacts related to new blocks being loaded - sometimes I'm under the impression that the game does some weird routine of spawning every object in the middle of the screen (on you) before "jumping them" to their correct positions, I've experienced several times this same issue where a lot of things started appearing exactly where I am when loading and then one by one they get teleported to their places (like walls, trees and even other people) - and that seems to happen when I'm using a lot of RAM on something else (like rendering a video file)
Overall I'd say it runs well, tho - performance never bothered me (even with shadows and such - and playing with more than one client) but I do see it as an issue because my home pc is fairly good and this is expected, but whenever I have to play on my laptop, which is average (not bad but not good either) the game looks horrible and runs as low as 10 fps in some areas.
So I guess that definitely shouldn't happen for a lightweight game like Haven

Knowing that jorbtar are working on client optimizations is very welcome news and I hope this thread shall serve as some good feedback

(edit: my specs are i7 from last year's gen; 16 gb ram, gtx1070)