Comment 33 for bug 629622

there are three ways I can think of to deploy it.
 * Set the interface font name in *gconf* /desktop/gnome/interface/font_name UbuntuBeta 10
 * Make it a suggested font in the ambiance and radiance *themes*
 * In *fontconfig* make it one of the fonts that alias to sans (tweaking stuff in /etc/fonts/conf.d)

Switching to the HighContrastLargePrint theme *suggests* a font which can be optionally applied and reverted. With gconf or themes this would mean highcontrastLargePrint would suggest sans, with fontconfig it would use the Ubuntu font family (I checked in #ubuntu-accessibilty, the new font is not seen as worse than sans for low vision use)

I am unsure what would happen if gconf is set to default to sans, but the default theme suggests ubuntu font family. I suspect it would use sans by default and in appearance-preferences you would be able to apply the ubuntu font - not the desired effect at all.

Using fontconfig to redefine sans means it would get used in documents as the default document font is sans. It could also reflow documents existing that expect sans to mean deja-vu-sans, they are not metrically compatible.

I would recommend changing the gconf key /desktop/gnome/interface/font_name and optionally the highcontrastlargeprint theme if you want all the themes to use the new font for the interface.