Actually I believe that partially dead pixels are a lot more common than people think. Many of us may have one or more but considering WUXGA contains 2,304,000 pixels finding the bad one can be tough. They are sometimes only noticable with certain colors. Try cycling your screen (with an empty desktop) through red, gree, blue, black, and white scanning the screen with a magnifying glass - you may be in for a suprise.
If you get a notebook with a bum pixel that is noticable then have DELL send you an LCD so you can do the swap yourself.