Correct camera rotation (Oculus Rift)

I was trying different approaches to use the second Xbox controller stick to implement camera rotation with the Oculus Rift. To do this I'm rotating the parent game object of the camera. However I was not getting a a fine result. It seems that the transform of the parent object and the camera get out of sync after a while. The camera scripts in the asset store seem to suffer by the same problem...

This was my last approach:
Code (CSharp):
  1.         void Update () {
  2.             // rotation by...
Correct camera rotation (Oculus Rift)