A week ago, I re-installed Arch Linux on my one of my computers. At that time, I decided to use GNOME as usual. But I changed my mind, why not have another Desktop Environment? Then, I installed KDE4.

It's just as if you run QT applications in GNOME, it must be ugly if you do nothing. You would see ugly GTK applications in KDE, too. Here is steps to prettify by changing themes:

gtk-qt-theme
  1. pacman -S gtk-qt-engine
  2. systemsettings/Appearance/GTK Styles and Fonts/Use my KDE style in GTK applications.
  3. Re-log in.
Matching the themes
  1. pacman -S qtcurve-kde4 qtcurve-gtk2 gtk-chtheme
  2. For QT applications: systemsettings/Appearance/Style/Choose QtCurve
  3. For GTK applications: gtk-chtheme/Choose QtCurve