I put one on my D4, from Zagg.
1) The gorilla glass is notorious for showing prints, which I cannot stand. Keeps it nice and clean also have a case on it so that overlays the ridge line so dust doesn't get caked in the edges of the screen.
2)Nothing is unbreakable. If there is a way for it to fall and scratch/break, it will eventually happen with my phone. Guaranteed. With my luck, I can drop a diamond from 2 feet and have it shatter on the ground.
But also, for those you having problems with screen protectors, having bubbles, falling off, moving, I used to never find one I liked either. But the InvisibleShield is perfect in every way. Basically, I stopped cheaping out and sprung for a good one and never regretted it since.