Comment # 17 on bug 965536 from Dr. Werner Fink

Beside of the trouble with the broken source/sink btween modesetting and
NVIDIA-0 the problems I've seen with the nvidia driver during debugging are
real that is the crash of the driver, the crash of the kernel module and/or
hardware GPU is real. That is even if the patch 
n_RandR-Disable-rotation-for-GPU-screens.patch becomes a smarter ome the nvidia
driver its requires IMHO some more work and *indeed* some more testing to avoid
crashes even if something goes wrong between modesetting and nvidia.