Two issues:
- when exporting to PDF, there is a listview widget inside an expander at the 
bottom of the GTK filechooser that is *always* open/shown by default. This is 
not the case with the GTK filechooser that shows up when you do a normal file 
"save as" operation
- more importantly: this widget is completely useless when using the GTK 
filechooser dialog, because it replicates exactly the same thing as the combobox 
that allows you to set the mimetype, just above.

This is a precious waste of screen real estate, especially on netbooks, and is 
also a bit confusing because the same functionality is presented twice.