Just sharing my experience at Genius bar with y'all in case any of you are in my same situation... I was able to pre-order my iPhone 4 and I received it on the 23rd. After syncing with iTunes, I went and started changing all the settings to what I wanted and I immediately noticed that I had a yellow spot on the bottom right hand of my screen. I also noticed that as I used it more and it got warmer the spot would spread upwards and stretch along the side. When the phone would cool down (usually at night time when it was chargning) I would check it and it was gone. I kept checking out threads on here and noticed some people had them as well. Then I read about the "compund/glue" theory stating that it didn't have time to cure. I waited it out and a couple of days ago decided to schedule an appointment before my 30 days was up. Today I went to the Apple store (North Point Mall in Ga), checked in and started running several apps on my iphone. I did that because (naturally) my phone was barely showing the yellow spot, I was trying to get it to show up so the Genius woudn't think I was crazy. I was finally called to the bar and told the guy (can we name names?) what the deal was, he said that Apple issued a notice to the Apple Store Supervisors that it was a glue compound that had to dry. I told him that I had been using it from a month. He basically just stood there and said 'uhhh' and then said that they couldn't "fix it". I told him that I knew they couldn't fix it and that I wanted to switch because I didn't want to end up being stuck with and then the yellow starts to spread more. He opened a drawer and pulled out the little black box with an iphone in it and started to put my sim in it, I asked if I could play with it for a few minutes before I officially signed off on it to make sure it didn't have spots and he said it was fine. I opened the camera up, recorded some video and a couple of other things and never saw a spot, so went back to bar, signed the sheet and walked out with my phone. 6 hours later, still doing well. I didn't come on here to brag, I just wanted to let others know just in case they are planning on returning/exchanging theirs.