Other than the new login screen design, I absolutely love the look of elementary OS. The theme is not flat, but it's not too bold either. The icons are simple but stylish. Everything seems to be in the right place. The animations are nice

I like Files and Music the most. Currently I can't use videos, but MPV is better anyway. Calendar looks decent too, and I don't use Mail.

Press Super + F, select a window and it will show that in the bottom right corner in a smaller window. It's a good option if you want something to keep on eye on, while you are doing something else in a full screen window. At the moment, when I write this post, I watch a twitch stream. This is a pretty cool option imo.

I know it's not really elementary's idea, since it comes from Gnome, but I still like the implementation which makes it easy to use. If you don't know, Night Light switch off blue light, after sunset, or at a specific time. It's pretty good for the eyes, and you can configure it from the panel, how strong you want to use it.

Consistent in design and philosophy, and only the essentials. Pretty refreshing from my KDE days, when even the advanced settings had advanced settings.