Careful, they break *very* easily. Compared to the strength of gorilla glass 4, tempered glass screen protectors readily shatter. I don't think they offer any shatter protection at all and from what i've seen in reviews of gorilla glass 4, i doubt the tempered glass hardness is helpful either:
https://www.youtube.com/watch?v=Oyx6PpXuJfc
Compare that with:
https://www.youtube.com/watch?v=mLD4hZlA4HQ
And you'll see there's good reason they don't use tempered glass on smartphones. It's just too brittle.
That said, you could still use a screen protector to reduce glare (such as a polarized screen protector). I use one for my glass laptop screen and it makes a world of difference -- instead of looking at reflections when i use it, i'm looking at the display. I also put one on my nexus 5 and found it helpful when in bright sunlight.