I had an ipad1 with screen protector. Never got a scratch, but I liked the anti-glare feature because it didn't show finger prints.
Ipad3, bought at launch. Bought a screen protector, but never applied because I was lazy and I decided since I had this thing in a folio case, I didn't have to worry about it.
Two scratches, both on the bezel portion of the screen. Wish I had applied the screen protector.
Search this forum, you will find hundreds of people stating categorically that there is no way to scratch the screen and that protectors aren't required. And you will find dozens of people saying they scratched the screen, even though they were careful.