I did a few tests of the new custom build release and compared it to what's still bugging me in 28.7 (addon version). Here are some results ...
WHAT IS BETTER/SOLVED COMPARED TO 28.7 (ADDON VERSION)
>> Faster scene compilation in geometry heavy scenes
This is way faster than in the addon version. But only in geometry heavy scenes. Here are some time comparisons ...
Sphere test scene (2500 spheres - same material) -> V28.9 - 3 seconds ... V28.7 - 20 seconds
Big scene (a lot of textures) - Initial compilation -> V28.9 - 50 seconds ... V28.7 - 49 seconds
Big scene (a lot of textures) - Subsequent compilations -> V28.9 - 18 seconds ... V28.7 - 17 seconds
>> Render icons are correct when switching workspaces.
>> Cancel renderings with denoise enabled works now.
>> ACES checkbox in the preview panel works now.
>> OCIO switching in and out of camera also seems to work.
>> Starting Blender without server running is a bit faster now (8s compared to 12s)
>> Adding Blender nodes in the Compositor works now.
WHAT STILL NEEDS ADRESSING
>> Bump discrepancy in Multiply node vs. Bump Height (but that's a Standalone version issue)
>> Capitalized wording in accordance with Blender style (but that's supposedly already done in some unreleased version).
>> Gettings rid of the new Camera Imager checkboxes. There has to be a better way.
So the first overall impressions are good. Let's get the addon version to that level and we are happy campers. I will probably find more issues, but I hope that an addon version will be released sooner than later and I will continue there then.
Addon tests were done in Blender 4, Windows 10, RTX 3060.