Well, sure it protects the screen when closed but what else can it do?
use it as a tripod to shoot upwards
use it as a tripod to shoot downwards
if you flip the mirror a bit upwards you can use it for ground floor or hip shooting
use it as a sun or rain block for the lens (sprinkles only)
use it as a sun shield to see the display better or to gain better access to take a shot
also good for over head shooting
use it as a mirror if you want to shoot yourself because nobody is around or if you want to shoot backwards (spycam)
Want to know more about the SMM?
Why don´t you head over to my HX1 blog and have a look there.