PSD can be used in Maya now, but the problem is it will be slower than regular image format when open the project and render.
MR doesn't support PSD format so it will cause problem when render.
"有時見到maya 一d 眼看簡單的野做唔到,會有點不是味兒"
Well, part of our job as professional is to optimize the workflow/pipeline in order to get the best result in the most reasonable time. Personally, I don't think saving the final PSD as tif or other format for render is that big a deal, I would do that anyway even if Maya's MR support PSD format in order to get faster render.