Also could be that people need to update their drivers, I'm on max settings and 1080p res and it runs pretty smooth mostly on 90fps if I dont turn on vsync, but every now and then I feel a micro stutter nothing serious. This game may not be perfectly polished but it's still alot better than most of the new games coming out lately..
It's probably been mentioned already but i expect nvidia users to be having fps issues given that this game was designed around amd's new mantle tech and being purposefully not optimised for nvidia gpu's but thats just my opinion.
Also it's about time something runs better on an amd gpu for once, after all nvidia decided to screw amd users with the Batman Arkham series of games.
Now i am not trying to start a flame war or anything here, but as i said this is my personal opinion.
Edit: if this is offensive for some reason please feel free to send me a pm and i will edit it myself, not like i want to get banned from here after 7 years.