I like software to be configurable and not designed for idiots. I want to be able to shoot myself in the foot.  I was put off gnome when they went the simpler-is-better (I-know-better-than-you) approach and the new kde seems to be taking a similar road.
A lot of key bindings are preassigned (not bad) and can not be changed (bad) because to do so would clash with some git’s preconceived notion of how to use a computer. Take assigning Ctrl-arrow to move around desktops which I’ve been using since before kde. Try to assign this in kde4 and you get an error:

The ‘Ctrl+Right’ key combination has already been allocated to the standard action “ForwardWord” that many applications use. You cannot use it for global shortcuts for this reason.

 
WTF? I switch desktops all the time, I don’t think I’ve ever felt the need to move the cursor forward a word.
Good software should be easy to understand and learn, but it should also be flexible - something that is often forgotten.
 
Luckily, it’s linux. Edit ~/.kde4/share/config/kglobalshortcutsrc to your heart’s desire.