Takes 6 seconds to switch to render viewport in 4.3, instantaneous in 3.6. Renders 2x longer. Anybody else seeing this?
Not exactly that one issue, but other issues pop up from time to time. Always a thing with newer versions. In that case I just go with 3.6 and work from there. Using the ultimate latest version is not something I worry about, though one does have to be mindful if there's a feature that wont go over next time I open it in a different version.
First, it takes longer to render the first frame since it need to load the render Kernel. After that it should be faster.
Second, If it's still running slow then ctrl+comma->system->Memory & Limits->Change Max Shader Complilation Subprocesses from 0 to something else. It really depends on your CPU, but it seems to work well set at 4 on my system. The max you should set it to is the max number of Threads your CPU has.(Usually 2 for every core, but not always.) Note: you will have to restart Blender after making this change for it to have any effect.