If the above suggestions do not work, try holding it upside down above your head and giving it a few shakes, sometimes that dust just never settles back just right.
But seriously, I am worried what the screen will be like 3-4 years down the road. My original iPhone started to get a line of dead pixels a year after I had it, now there are two nice lines and spots. Thankfully I don't really read on it much, annoying in some games though.
My 60GB iPod Video (about 5 years old) just a few months ago started to get sime dead lines as well, and my mom's iPhone 3G got a few spots about a year after she had hers. Yet my iMac is flawless 4 years later.