I've never noticed any, though admittedly I haven't run any specific tests.
A friend of mine - coming from Audio Applications working with ProTools and Logic says, that Gain always require resample and new quantization that results in quality loss...?! I don't hear any difference...!?
He may be right, but not all degradation is noticeable to all people. Most of my family have no problem watching an image that drives me nuts with artifacts.