I think mirislav has some good points. I do agree that there are some game breaking bugs, but system settings can play a big part in things as well. Some players expect things to be dead on perfect out of the box, and that isn't realistic as we all know. Personally, I have had no issues with the game except for some really minor thngs that were in no way game breaking, such as Geralt partially disappearing into a rock wall.
People tend to complain when they totally ignore system requirements and don't have the system to play the game. There have some games that for sure were so buggy that they deserved the criticisim ( Fallout: New Vegas comes to mind ). I have had no problems since I installed patch 1.3, but then again, I installed it last night and didn't play all that much. As Kindo said, it seems to vary from player to player, which leads me to believe that it is system related to at least some extent, as everyone has a different system configuration.
The only frustration I have ahd was just playing the game. I wasn't paying attention when I set it up and started playing on what I thought was the easiest Mode. Couldn't understand why they would make something so hard in that mode. As it turned out, I was in Hard mode and didn't find out until way late into the game, so left it that way. Have completed a second playthrough in Hard mode as well, but it wasn't as frustrating.