I've recently fitted a glass screen protector to my iPhone 5. I'm not the first but I thought I'd post here to say how much better it is than the plastic films that I've previously used on all of my iPhone models.
It feels really smooth and there's no initial resistance to polish out with use, as with the plastic films. It is about three times thicker than a plastic film and the kit included a stick on button to go on top of the home button. The home button was useable without the additional stick on one but there are obviously implications for use with the 5S. Someone would have to try the fingerprint reader to see if it is hindered by the additional screen thickness. Obviously the add on sticky button isn't an option for 5S. Probably rescanning the thumb with the glass screen protector in place is an option.
The kit was £3 from eBay (an auction, not buy it now) and included:
3 alignment stickers
1 dust picking sticker
1 black home button sticker
1 white home button sticker
And of course the glass screen protector
It's in place, completely dust free and the phone works with perfect response.