Your Firefox (Iceweasel) looks really bad under KDE 4? Wicd and Gimp are ugly? Thunderbird (Icedove) borders, buttons and menu are broken?
Tweaking Gnome Apps to change theirs look & feel on KDE is simple. Follow three steps described below and repair almost all GTK applications appearance under new KDE.

Tweaking Gnome applications under KDE 4 on Debian Sid (Solution of this problem with other distro should be similar)

1. At first open konsole and type there:
   sudo aptitude install gtk-qt-engine-kde4 kwin-style-qtcurve kde-style-qtcurve gtk2-engines-qtcurve
2. Configure KDE. Open: K menu->System settings->Appearance. Choose GTK styles and fonts tab, and select there:
   
   • GTK styles: “Use another style: QtCurve
   • GTK fonts: “Use my KDE fonts in GTK applications”
3. Click Apply and reboot system. After reboot your Iceweasel should look like on screen attached below.