Can anyone confirm that custom fonts are supposed to work on a non-jailbroken Kindle Keyboard (global 3G) running v3.4?
Using calibre 0.9.14 and the plugin from the OP, I can select a custom font (tried Georgia, New Baskerville and Droid Sans) successfully and enable the user font option. After rebooting the Kindle, the font menu changes from
regular | condensed | sans
std | sans | mono | alt
where std and sans work as before, but mono and alt both show up as the default Kindle font. Selecting std causes the menu to revert to its previous configuration.