well a sealed phone can not be checked.and ya it was all fine.untill the next day a big white screen came on..and when replaced then at night in dark i see some black marks in the screen..u cant even see the darks now.

even ther is red camera spot..which is somehow in every peice

ok here the links
http://www.google.com/support/forum/p/Android+Market/thread?tid=7a1e2951b341823f&hl=en 
http://www.youtube.com/watch?v=hCfxCdtgxVw 
http://www.youtube.com/watch?v=LfMeK_18TmE&feature=related

read the comments in the videos

and a bunch of them
http://www.facebook.com/pages/Samsung-Galaxy-S2-screen-Issue/124708717610574