Opening files automatically on mainstream Linux desktops

Xfce/Gnu/Linux works amazingly well on my moms workstation, with one exception: opening files automatically with the correct program.

The two biggest culprits are:

• Gtk's "open file with" dialog: if any Gtk program doesn't know how to open a file it brings up this dialog that is horrible to use. You can search through your entire VFS for the right executable. No thumbnails, no usage of .desktop files, $PATH, autocompletion and not even limiting the scope to directories such as /usr/bin
• Mozilla software such as Firefox and Thunderbird: they only seem to differentiate files by their mimetype, not by extension. There are add-ons to make it easier to edit these preferences, but eventually you're in a dead end because you get files with correct extensions but unuseful mimetimes (application/octet-stream)

Luckily the fd.o guys have come up with .desktop files.
In $XDG_DATA_HOME/applications/defaults.list you can define which applications to use for which mime type.
So the only thing you need to do is call xdg-open to open a file with the application you want.
And that's exactly what I did. For now I just configure everything to use xdg-open and that seems to work just fine. Oddly enough, even though the defaults.list is also based on mimetypes, files that are marked as octet-stream in Thunderbird seem to be properly recognized by xdg-open and opened with the correct program. Or maybe this is because at the time of testing I only had octet-stream .doc files. Anyway, we'll see. But for now it's looking pretty good.

Note: somewhat related and also not very pleasant: epdfview used to say 'encrypted document.. please enter password' whenever you tried to open a non-existent file, a directory,.. basically anything else then a pdf file. But this seems to be fixed since 5 days ago.