I have played 6 hours on pc with all settings cranked to ultra with nvidia hair works on as well. the game is mostly 60fps. theres a framerate issue during cutscene which is bug . Apart from that the only i notice it , is when you ride roach too quickly from area to the next. I have had no problems with game breaking bugs as mentioned on the internet.
The graphics is purely stunning. The story is fantastic and the detail on the npcs and the main characters is wow. Oh yea yennefer on ultra is damn fucking hot!. Combat is much faster and much more responsive then witcher 2. Leveling up system is very detail and follows skyrim with light, heavy an medium armor. Mutagen plays a bigger role here with your character stats and how bonuses given by the mutagen increase if you match them with the abilities you unlock. AI is pretty smart.
You don't have to worry about them. Difficulty hasn't changed from witcher 2. At the start you are alot stronger then you were in witcher 2. Plus no loading screens is awesom. Btw if you have purchased the retail version of witcher 3 , then you have to install 4 discs. The graphic options available is not as big compared to witcher 2.
The hairworks is pretty cool. they work and looks Quite realistic. it works on geralt and the enemies. Its still not proper which you guys will see as you progress in the story. If you dont have a top end GU, you will get quite a bit of performance hit to your frame rate
my impression i wrote on the witcher 3 meta thread