I saw the film in 2D, because to hell with these newfangled shenanigans, but I imagine the effect is worse in 3D. Further, I am not, as a rule, susceptible to real or imagined motion sickness; I have excellent sea legs and have never felt even queasy on a 'plane.
Erebor was over-saturated, swoopy garbage. I enjoyed the aesthetic choices (notwithstanding the lack of basic practicalities), but the effect was sick-making and false. I had thought some precautions were taken to obviate the CGI failure, but apparently not. The colors looked unreal and something between the screen and my brain did not connect.
Look: this is kind of the point of these films. If you're going to take liberties with the book, you need to be pitch-perfect on the effects. It's fine if they look dodgy in a decade as our eyes and sensibilities catch up, but they need to look great right now.