keepitwarm: No! Don't do it, I took my gecko clear ( yes those are ok) protector off in the pub one night as the corner lifted, my fault, anyway went out next morning forgot and scratched the screen on my 4, after only 2 hours just forgot and put the keys in my same pocket, not a deep scratch or anything but enough to piss you off and noticeable but the screen look and feels better without it, don't think it worth possible scratching it with a bit of bad key pocket action. I'm normally very careful.
I scratched the screen on my iPhone 4 with some keys in the same pocket too. I don't like screen protectors but they're less annoying than a nasty scratch on the screen. Just wish I could find one that felt ok. I used to have the invisible shield ones by Zagg so may try one of thos again although they do feel quite sticky