A hook has all but if you want to get the iPod out of a tight jeans, stops the silicone and pressing / pulling the iPod may require a little out of his jacket out. Actually no big issue: simply push back, but sometime annoying that.
The key lock on top of the iPod is more difficult to achieve. It now requires either a little smaller or a little more finger fingernail (no sausage fingers). The thickness of the silicone shell is 1 to 1.1mm.
Postive is definitely that the player is protected all around; (but protector included) up to the cutouts for the display, recess for the jog wheel and of course cutout for the camera on the back.
I think if you do not let him fall (or at least the risk does not pass) ranges from a simple screen protector.
