I have not had a chance to try Expert RAW properly yet as am waiting for a London city day/night photography walkabout in a few weeks, but for normal mode I am finding that Lightroom produces slightly cleaner results off the photos on this phone than what I had with the S20 so far.
There are still a few things that are slightly annoying to see have not been upgraded from the S20 like not being able to switch lenses when recording in 4K 60fps, you can choose the lenses, but once you start recording you are stuck with that lens. As a result I use 1080p 60fps as that works fine switching lenses and is actually smoother/cleaner and focusing is faster.
Overall a marked improvement especially for sharpness and AI improved portrait mode. I expect many more improvements will be seen in months to come with updates but so far so good.
Edit*
The edge display where the screen curves off the edge, some initial reviews said it was annoying and they didn't like it. I have noticed no issue at all and until now I had not even noticed that it wasn't a completely flat display. An issue hyped up to add controversy in a review I guess.