Since the focus of realtime preview development seems to be on Nitrous features currently instead of on ShaderFX/DirectX shaders, it would be beneficial to add support for roughness/smoothness maps. The other crucial preview features (normals, metalness, AO, shadows, HDRI maps) are sort of there like Mr Eloi Andaluz showed in his recent, great video. However, the lack of accurate roughness still makes the materials look a bit off compared to an actual render / PBR shader preview.
Nitrous can provide good-looking previews which is very nice, but certain shortcomings such as this (and lack of planar reflections for example) still don't really make it a viable option for proper rendering of materials. Real-time previews in Max viewport still need more love in one form or another.
