Also on-off button and volume rocker are exposed so that the knobs are first, easier to use, because it is not a rubber coat over it is, for example, and are second, even blind to use when the mobile phone during music listening in the bag and draw a want to make songs quickly up or down, without getting the phone out of your pocket
The back is slightly rubberized, so the phone is not so easily slip out of hand.
But you have to really work with millimeter accuracy when sticking a protective film because the shell logically surrounds the sides and therefore to curl the film, if it is not flush with the edge of the envelope.
Unfortunately I have no experience of how the shell behaves in a fall of the phone, but here is probably true, which applies to all cases: They are designed to protect primarily against scratches and there is never a guarantee that the phone (and here especially the display) a fall of 1 meter survived. I would, however, take a chance even when no cover on it.