Often when people complain about the max viewport vs say the blender viewport capability its because most people arent using native renderers in max and therefore the viewport support isnt as complete as say the max physical material might be.
Id love to see greater compatibility between the max viewport and corona materials and maps. Probably not a priority item but it would benefit my workflow greatly being able to show more complex material graphs in viewport without needing to render or use IR for design reviews in real time.