After moving to KDE three weeks ago now, I am staying. At least for now. If I had to pick on something, my main point for feedback would be that the graphical user interface feels crowded, and its usage metaphors, albeit consistent, are rather complicated.
In KDE, configuration options are scattered all around the place. KDE is a great platform for the power user, familiar with tweaking and working with plenty of configuration options, but for the rest of us who just want to get on using the applications and not waste our time fighting with configuration options, a simpler paradigm for desktop and programs alike would be more useful. That simplicity is one of the design goals of Gnome: sane defaults, clean UI and few configuration options. Unfortunately Gnome has gone too far, and makes it sometimes either impossible or very hard for the power user to configure the desktop or an application to its own liking. While preserving for KDE’s power users the current ability to configure practically anything, the majority of users would however benefit from a cleaner and more modern user interface metaphor.