For those too lazy to click the link:

Beyond the UI refinements / workflow improvements, some things that stuck out to me were:

Core: Make it impossible to have more than one main thread, and don’t release unnecessarily (GH-121161).

Core: Speed up removing many child nodes (GH-120942).

Seems important, and good. Probably not a good idea to somehow have two main threads racing each other.

Also we all know killing your children as efficiently is possible is what makes games fast, lol.

Editor: Show doc tooltips in quick settings (GH-121278).

Input: Ignore joypads on unfocused window by default for new projects (GH-120399).

Both of these will definitely reduce headaches for me.

Rendering: Use non-volumetric fog in WorldEnvironment sky reflections (GH-107958).

Another very good optimization.

Thirdparty: Update to Jolt Physics 5.6.0 (GH-121260).

Possibly a big deal if you run a physics intensive game.

I am guessing implementing the new hair physics would not be on the table until 4.9, but, Jolt 5.6 overhauled its friction calculations to be more efficient, so... that could be a blessing and a curse, might make your physics setup need to be re-tweaked a bit, but should also be significantly more performant.

More on Jolt 5.6.0 here, not sure exactly... how much of this would be fully supported/utilized in Godot 4.8. 'Upgraded' is kind of sparse, so my guess would be... just whatever Godot is currently basing off of Jolt will be migrated, and the new features, new cpu/shader stuff... ???

https://gamefromscratch.com/jolt-physics-5-6-released/