After eleven years and a bit, I think I stopped.
Alt-F2 was too slow, and the application serving it ate 400MB RAM including all the shared libraries it didn't actually share with anything. RAM may be cheap and maybe I can spare some of my 4GB, but I detest using 400 MB in order to handle Alt-F2.
Alt-Tab and Control-F1/2/3/4 were annoyingly slow, and sometimes when I switched windows (e.g. control-f2 alt-tab) and immediately typed into the target window without waiting for the screen to refresh, the keyboard locked up and I'd have to log out and in again.
No idea whose fault that was. I think there are several bugs in that area, some not in the KDE, some probably in the KDE. It was damned annoying anyway. I'll try using xfce (with konsole, xemacs, konqueror and opera as the main applications).
plasma thing introduced in KDE4 did strange stuff I could not understand, and stupid things I hated. What were those things that looked like angle-brackets, what did they do? Why did the clock not support Indian and Nepali time zones? Why did the settings stuff pop up tiny dialogs with scroll bars in the middle of my pleasantly large screen, and wouldn't even let me resize? Windows is supposed to use mindless keyhole dialogs, KDE not.