I don't know how many times I've had to install 100's (ok it seemed that way) of gnome apps just to tweak the font's in GTK apps so that they looked decent. The KDE apps have always looked good. But the GTK ones lacked, well, everything.
Then I ran across this little article on how to do it. All I had to do was run this command in a term window.
#> sudo ln -s /etc/fonts/conf.avail/10-autohint.conf /etc/fonts/conf.d/
Then I restarted the X server, and the fonts on GTK apps (Like Firefox) began to pop like their KDE brethren. HTH