I tend to be fairly careful with my iPhones, but I've owned 3 previous iPhones, never used a screen protector, and never had a single scratch. They are pretty impervious to scratches, although if you toss them in your pocket/bag with keys or something I don't know what would happen (I dedicate a pocket solely for the iPhone at all times, nothing else ever goes in that pocket). Of course scratching and breaking are two different things, iPhone screens will most certainly break, but a case will serve you better there than a screen protector. I wouldn't recommend using one, but it's up to you. Some people like the matte surface screen protectors to reduce glare, but I hate the look of the screen under them and the feel with your fingers is not as good IMO as on the glass.