I absolutely detest screen protectors. Everyone and their grandmothers have an iPhone, and majority of them with screen protectors that basically mess up the brilliance of the screen.
I only use a decal to protect the back and to make it look pretty, and every now and then I'd get people exclaiming at how awesome my screen looks. I HAVE THE SAME PHONE AS YOU PEOPLE, STOP COVERING IT UP WITH ANTI-GLARE OR WHATHAVEYOUs.
Get a proper cover or casing for the back because it scratches quite easily. With the iPad especially with its large real estate, an anti-glare sheet might give you some privacy when you are commuting, but you lose brilliance of colour and image to yourself at the edges sometimes.
I had an iPhone 3G for 3 years. There were some minor scratches on the screen but I was abusing it so much, the back was basically scarred from the many things in my bag because I just throw it in. It also survived a trip into a toilet bowl; no water marks beneath the screen and all. (NOT RECOMMENDED)
Sorry I sound ranty, but I love the screen and it's a travesty to cover it up. Just don't assume the screen will not shatter into many pieces, because it will. But the screen protecter will not prevent that, only a proper case would.