No screen protector on my iPad 2, had it out and about, used it like crazy, let others use it, not even a micro scratch...glass is perfect as day one!
Had a screen protector on my 4s, got tired of it looking so bad after a month, took it off and been very very happy, I use a speck case, and even a few falls on cement and it's still perfect.
I no longer recommend screen protectors for an ipad, iphones maybe if you always put in say a purse, or pocket with sharp objects, or just drop it all the time.
I say go naked.