The default behavior of the file manager (always asking if you want to move or copy the files) might have been the only quirk that took some getting used to when I first started using KDE a few years ago. In the end I got used to it, even prefer it (you can hold shift or control while dragging to automatically move or copy), but it's nice that it's configurable now.

Kde is the only software project I've ever seen that gets better and better over time.