So I purchased the 27" the third day it was released... after the latest firmware update, I experienced some pretty bad flickering, screen wasnt yellow at all, and everything else worked beautifully. I made an appointment at the genius bar to get it looked at. I calmly explained to the Genius that I was a student and simply couldnt afford to go without my Imac for any length of time. He hooked up my Imac and ran it through a series of tests, and of course, the Imac wouldnt flicker! He ran multiple programs simultaneously and it wouldnt flicker. Finally, after about 25 minutes of running 8-10 programs, it flickered a tiny bit. He went and spoke to his manager, and they swapped it out on the spot! He took my Imac back, and handed over a brand new, unopened box. The new Imac is fantastic! I was very pleased with the service.