Coming from an IP5, I always used a Zagg screen protector. When I got my One, I so liked the screen feel I did not put a protector on it. I do have the Poetic Atmosphere case on it and love that! Anyway, I went biking a few weekend's ago and my wife's screen got a bit scratched and mine was right next to hers, so I ordered the GLAS.t SLIM protector. I was a bit leery after reading some reviews, but went ahead and put it on last night and really like it. I washed my hands and ensured the screen was pristine. I did not have to take the case off, it went on super easy 1st time. I just lined up the bottom and pressed down the middle. I had 1 bigger air bubble, but pressed it out. Today I have 1 very small one, but I think it will go away. The touch is like the One screen, no issues at all with back or home press. I did have the AT&T software update< i heard if you did not it may be decreased sensitivity.
Anyway, I'm extremely happy with the protector, its invisible and feels just like the original screen.