When I upgraded from Debian 12 to 13 on my personal laptop running KDE, I knew that the switch from X11 to Wayland would happen and was braced for all kinds of issues, like every other time I tried to switch to Wayland in previous years.
Instead, I could tell literally no difference. Multiple desktops works fine, scaling works fine, screen capture works fine, old apps work fine, literally everything works just fine.
Good job, KDE team.
I think I noticed lower latency, more consistent frame pacing (recent-ish improvement in KWin) and a more "solid" feel because everything in a frame is synchronized. On X11, you can have things like border and contents of a window not matching exactly while resizing. An early principle of Wayland was "Every frame is perfect", which is clearly reflected in how e.g. window resizing works.