I like the new sidebar look. Finally has some color again, at least.
I like the new small folder icons. They pop more than the previous ones.
Control Center is a nice idea, but its interface was clearly not designed for a cursor, and nothing else in the OS looks like it.
I despise the new title/tool bar. There's no clear separation between elements since the buttons have no backgrounds or borders anymore. The way the window title is in the same row as the buttons means its location is inconsistent across applications, as opposed to always being top and center as it was before. Now it's sometimes immediately to the right of the traffic light buttons (Activity Monitor), sometimes immediately to the right of the sidebar (Mail), sometimes immediately to the right of... whatever variable amount of buttons happen to be to the left of it (Finder, System Preferences), and sometimes centered (Terminal). Both of these issues makes the whole OS seem very messy.