... it would do exactly what it said on the tin.
It's a screen protector, it appears to be protecting the screen. I bought mine at least six months ago and have only applied two in that time, the one that's on now has been on there for ages and looks to be quite happy.
They're at least as easy to apply as any other half decent ones. I reckon that if they don't go on very well it was probably operator error. The first one I applied managed to pick up a speck of something which left me with a little bubble, it was okay but was ultimately the undoing of that particular one. It still endured a couple of months or more.
The phone, on the other hand, is a completely different bag of spuds. Every time I activate the camera it reboots the damned phone! They said I should upgrade to the latest version of Android. Oh yeah, that was fun. I could have forgiven the pain if it had given any improvement!
In summary, the screensaver is much better than the phone it is protecting!