nvidia-settings GUI wrong temperature reading
The temperature reading of nvidia-settings GUI of the 256.35 driver seems to be off by 10 degrees, e.g. the GUI shows 64 C while the result from the command line is
nvidia-settings -q [gpu:0]/GPUCoreTemp
Attribute 'GPUCoreTemp' (extragalactix:0[gpu:0]): 54.
The latter is the correct value for my almost idle system.