Hmm, just played with this and couldn’t get much to work at all.
Having it activated also seemed to disable the WordPress.org language packs for the theme.
I’m not sure if there’s something specific themes have to do to integrate with the plugin, but it didn’t even seem to work on the site title which is handled 100% by WP.
If the plugin author has any suggestions for what I can do to make GP compatible I’d definitely listen, but it might be worth checking out a couple other plugins as well.