I made some adjustments to retain the calibration and overall image quality, it should be pretty much identical with the stock kernel now.
The difference is basically the increased visibility of mura defects without PWM (flickerfree kernel behaviour) or almost no visible mura defects with PWM enabled (stock kernel behaviour).
Here is a quick comparison photo:
(Stock kernel is on the left side; if you look closely you can see the some repeating transversal lines, those are the typical PWM lines captured by camera.)
(Flickerfree kernel is on the right side; there are some bright dots that looks like compression artifacts, those are mura defects.)
Here is another photo for a better comparison (left side: mura defects masked by PWM, right side: visible mura defects due to missing PWM).
(Note: those mura defects are especially visible on very low brightness <20cd/m2, anything above 40cd/m2 shouldn't be noticeable).
More information about can be found in the Samsung AMOLED patent description: Organic light emitting display device and driving method thereof