Few more questions on the picture:
1) Can Reflection Color brightness be higher thatn 100%? Maybe should we use 0..1 range in place of 0..100% ? 0..1 is easier to undestand when all the shader input/output are in these absolute values (not percentages). I believe it would be easier with this considering existing math shaders and more future shaders especially when node based shader GUI will be out.
2) What invert checkbox is doing? Is it an indicator that switches between constant and shader property?
3) All the properties will be with shaders/textures including Fresnel IOR and Aniso rotations. Cool things can be done with that.
4) Displacement will not be here but probably in another material like current multi-material or separate "geometry_shader" which will be assigned as tag for an object.
5) Will highly likely add the dropdown selection of mixing mode for material layers: "stack based" (like now, higher layer override lower layers) or "weight based" (like people used to, everything is relative to each other).
1-The colour slider shouldn't go higher than 100%.
The only colour parameter that should and must is the one from the Emission channel.
I'm OK with having it between 0-1 instead of 0-100% if that facilitate your work. Others might have different opinions, though.
2-The Invert checkbox serves to invert on the fly the grey scale images used on certain parameters. This speeds the workflow.
4-Is a current limitation the fact that the Displacement channel, can't be used on the "regular" material?