Actually, I think that's perfectly normal. There's a plastic strip along the top that's likely for the antennas, and it's definitely curved. I checked a number of SP3s (a few I had and the ones at my local Microsoft store) and they all have it. In fact, that's why it seems like there's some screen separation on every SP3--the glass is straight (natch), while the plastic is curved, and so the glass protrudes a millimeter or so towards the middle of the plastic component. To my mind, it's nothing at all to worry about.