In the new 12.1 I get awful looking fonts in GTK apps under KDE. IN the olden days I used gtk-qt-engine to control this, but now it is kcm-gtk (or whatever the module is called). Under 12.1 it seems to work with some software and not others. I have read that this is a gtk3 problem (the kcm module only working with gtk2?). Anyone know how to fix it (I have tried the gtk fonts bit in the KDE control module, which worked under 11.4). Firefox in particular is the problem. Menus etc look rubbish.
The Muzlocker repo significantly improves the OpenSUSE fonts especially for GTK and Mozilla products such as Firefox and Tbird. I ran Ubuntu/gnome2 until Unity ran me off and now I am a very happy OpenSUSE/KDE camper. My fonts are outstanding and everybit bit as good as Microsoft/Ubuntu/Mint, etc… See: