I still have the screen protector on my screen from the first day I got my phone and it still looks great. I have the rest of the protector pack still in the Box the phone came in. With my *Speck red and black case around the phone, it still looks new!
I used a Zagg for probably almost a year then for some reason one night decided to peel it off...so glad I did. I had forgotten how smooth the screen was and how easy it was to navigate with. That was probably back in february and I'm still scratch free!
I have on a Stenheil (?) screen protector...it was crystal clear for a very very long time, really looked like an unclad screen...it's finally scratched up enough to be noticeable...guess I should take it off. Or put on a new one. Even that thin layer adds alot of impact protection for when I inevitably drop the phone.