We put the ZAGG invisible shield on our smart phones plus Janet's Kindle Fire. I am very hard on my equipment and there are already scratches on the shield. If it gets a bit more scratched they will install a new one for about $5. I have not seen any preformance issues on my G3 but on my wife's phone it seems to make the camera function a bit harder to operate but she is used to it and has no issues. I also installed a 2 piece case for the G3 that I got from Verizon like this:
Hard Case This puts the screen inside the case at all times when not in my hand and it has saved it when I have dropped it but there's not really any sort of cushioning effect.