For selecting the video file to save to, gtk-recordMyDesktop uses the deprecated GtkFileSelection. For the working directory, it already uses GtkFileChooserDialog.
To provide a consistent visual apprearance and drop deprecated elements, I wrote a patch that replaces the FileSelection by FileChooserDialog in rmdSimple.py.
(While doing that, I found a use of FileSelection in rmdPrefsWidget, in __fileSelect__. I haven't found any use of this method, so is it just a left-over? Or have I overseen something?)