Hi Pokoy & Monkriss,
yes, the issue you noticed is correct.
This is why I switched back to the Beta from 21.12.2017. - Core 1.7 hot fix 2 !
Works great and - as you say - provides muuuuch quicker previews, since the denoiser is applied equally on all surfaces.
For quick renders we don't need crispy bump maps, right? We need images that don't fall apart in areas that are already smooth and bump map areas that stay super noisy even after many passes.
Also displacement stacking works perfectly in Core 1.7
Yesterday night I tested the new Corona 4 (Beta).
Denoising over the new integrated CPU AI - denoiser seems to deliver okay results!
Also displacement on stacked materials and poly selects works nicely in Corona 4 Beta.
As far as my test...
Testing right now on a more complex scene that was previously made in Core 1.7 Beta.
It seems to have some problems with converting textures, when opening it in Corona 4 Beta - like metals with maps on specular. It doesn't interpret the specular-maps correctly, especially if they are in a filter.
Also HDR on Sky objects don't work properly - only after you erase the old HDR and create a new one with the same HDR-texture.