Related question: anyone using an IPS or PLS panel noticed "IPS glow"? Since IPS panels are substantially brighter than TN, there's a phenomenon where corners can seem "lighter" due to IPS glow depending on your viewing angle, which is basically because the backlighting is so intensely bright on IPS panels (and like mentioned, much much much brighter than TN).
I think this is why many IPS panels opt for an aggressive (ie: very thick) anti glare coating, typically being much thicker than the AG present on most TN panels. To prevent the IPS glow phenomenon, I could be wrong though.