The release of the KDE SC version 4 series hasn’t been a success story in the first place. The first versions of KDE 4 are known to be buggy and slow. But the situation is constantly getting better. And since the release of KDE SC 4.3, it may be stated that the KDE software collection is quite useful in a productive environment. However, although the performance of KDE is constantly improving, it has never reached a state so far where it felt completely fast to me (such as GNOME, KDE 3, or lightweight desktop environments like XFCE, LXDE, or fluxbox do). A little bit of bubble gum always remained.
Until I found the »raster engine« of Qt.