After getting fed up with the borderless menus of gtk3 nautilus of gnome 3.4, which result in black text on light background on top of more black text on light background, I then find that all the CSS files of the default gtk3 theme have been unhelpfully lumped together when installed as gtk.gresource, preventing you from editing them.

Or at least it prevents you from editing them quickly, because you still have the source. But you have to fiddle around creating a patch, building a new rpm, installing it, seeing if it worked, and repeating as necessary.