So, here is how I find this problem with the screen, you could do as following to see if you have the same problem too: open "System preferences", choose "Universal Access" click the "options" button in "zoom" area, choose "continuously with pointer" press the "control" button and scroll with two fingers to activate the zoom in function, to exaggerate the problem, you could zoom in to the limit. now, move the pointer quickly in my case, i could see a horizontal line on the top of my screen as if it could not refresh as soon as the other area of the screen. i went to genius bar for help. Before that, i tried some of the models in the store, but none got that problem. Eventually one genius examined my screen and ran some tests but he could not tell if it was even a problem. He suggested me to continue using it and he would report this problem. I don't know if it is typical or what. I think it may be a manufacturing flaw. Is there anyone having the same problem on MBP 13' Mid 2010?