@theluthier I'm mixing in the "Anisotropic Shader" in Blender 2.90 (set to "GGX") with a factor of 0.05 (which is 1/4 th of what you chosed in the video) ...
... and get this result in "Preview Render Mode":
The factor of 0.2 chosen in the video for mixing in the "Anisotropic Shader" is too strong in Blender 2.90:
In Blender 2.66.1 there was no posibility to chose a calculation method, but it seems that even more has changed. So what would be the best settings?