Using 12.10, I can apply all but the last line in this answer: How do I change fonts and adjust their size? to change font sizes.
gsettings set org.gnome.desktop.interface document-font-name 'Sans 10'
gsettings set org.gnome.desktop.interface font-name 'Ubuntu 10'
gsettings set org.gnome.desktop.interface monospace-font-name 'Ubuntu Mono 11'
gsettings set org.gnome.nautilus.desktop font 'Ubuntu 10'
gconftool --set /apps/metacity/general/titlebar_font 'Ubuntu Bold 10' --type STRING
The last line referencing gconftool has no effect on window title font size. What is the correct command?