I gave material layering system a spin in 4.19 and overall I don’t expect any significant benefit from it. At least not within a scope of projects currently within my reach.
Firstly, changing existing uber shader in a more or less developed project to work with new material layering seems a bit on the painful side and definitely not worth the effort.
Secondly, With the way I’m building master mats, I could hardly find few occasions where matlayer system would be more convenient, than existing set of material functions.
Thirdly… well, there is no thirdly.
I see potential for the system only only in two directions. First being fresh projects made from scratch, where all the planning was done with the system in mind.
Second being a usage case where all asset texturing is done exclusively in the engine, potentially involving baking blended mat attributes into textures.
That is my impression so far.