PWM is used to dim the screen when adjusting the brightness. The lower the brightness the more likely you are to see flicker. PWM can cause eye strain, headaches or nausea. There may be more symptoms but I am not sure.
Testing out a display with PWM is the only way to tell if you are susceptible to it.
I had headaches using the Asus and it was not something I could put up with as I spend a lot of time on it.
Just testing out the VP2770 as we speak and its great so far. No dead pixels.

Back light bleed not an issue so far but not tested this out fully yet.
Out of the box settings are better than the Asus as well.
Going to try some games now and see how they look.