My phone got the update one week ago, and even if there's not much changes or new features, the smoothness of One UI is soooooooooooooooooooooooooooooooooooooooooooooooo much improved for me! Animations seems a little bit longer, but I see them from the beggining to the end, it doesn't cut at the half like it did often in the past, and they don't lag! Dark mode launches is faster, and doesn't cause luch lags when the active app is switching from light mode to dark mode. The charging animation is also improved, even if there's still no screen blur. However, autonomy is slightly worse than before, but nothing dramatic. Also, when I switch between the two types of navigation bar, I feel like if the phone stops working for a few seconds, whereas before it was just very slow. I haven't tried to use face unlock with an animated wallpaper, where the face was laggy and the wallpaper's animation stopped if the phone couldn't recognize my face and unlock the phone.
Edit: live wallpapers seems to stay animated when using face unlock (edit of the edit: finally it's not fixed)
Another positive point: rotation between portait and landscape mode is faster and less laggy
Another negative point: the phone seems to overheat a lot more recently
