While most of us associate PBR only with mirrors and shiny metals, there is a lot more to it since all surfaces benefit from it. The top pic here shows the room with the old standard (blinn phong) textures and materials taken using the FS 6.6.17 viewer, while the bottom pic shows the same room with all pbr textures taken using the FS 7.1.11 viewer. Note that you can add both texture sets to a surface so that any viewer can see something. Also note that there is a reflection probe filling this room that prevents the blue light outside from seeping in (a current known bug being investigated).
Saturation, lighting, and detail are significantly improved across the board when all surfaces are pbr, which is what Physically Based Rendering was designed to do: to more accurately capture the interplay of light on various surfaces. For those wondering about how performance was affected, these were taken using my 8 year old desktop that has a GTX 1070 graphics card. I was at 40 fps on ultra graphics, but you don't need to set the graphics that high to get this look. That's because the new viewer is more efficient since it uses more of your computer's available resources.