I mainly noticed the improvement while multitasking. On a normal phone I wouldn’t care as much, but on Samsung Galaxy Z Fold8 it makes sense.
The three-way split view has been surprisingly useful for me. One UI 9 makes better use of all that screen space.
I like how smoothly things move between the cover and main screen. It feels less like two separate screens.
Yes, it feels properly designed for the Fold. The larger screen makes the new multitasking options much more useful.