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I've not used screen protectors on my 2 yr old 4s, and the screen is still in great shape.

This has been my experience with the 4S also. Nary a scratch. Gorilla glass is so wonderful. I put a green bumper on the phone, and I do try to remember to put the device into a Waterfield sleeve (that suede one with the mesh front pocket for earbuds or whatever) in order to protect the ports from stuff in my handbag, but that's the full extent to which I coddle the thing. I did actually order screen protectors for it, and had used one on my 3GS, but with the 4S I just never bothered installing it.
 
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