On some X installations, the default GTK font size can be very small. If you want to increase it, add this to your ~/.gtkrc-2.0:

gtk-font-name = "Sans 14"

This will change the font size of the default font to 14 points.

If you get strange locale errors when running perl and GTK apps, run these commands and be sure to generate all en_US locales:

$ apt-get install localeconf
$ dpkg-reconfigure locales