Try stressing your phone out by using intensive apps for a good hour or so, A good way i found way just using maps to help my friend navigate to get to the apple store. Back of the phone became very warm to the touch and in the bottom left of the screen a yellow tinge was very prominant. If i look at my phone now ( haven't touched it for an hour or so) the screen is perfect and the process can be repeated. My guess is that some people dont even realise they have the yellow screen, or thought it had fixed its self the next day as they aren't using the phone as much as they did on the launch day. And also, is it standard practise that if you are slightly late for an appiontment at an apple store (just shy of 10 minutes due to traffic) to be told sorry, we can't see you come back tomorrow. Thanks for wasting over two hours of my life In the end i phoned the o2 shop, as i dont wish to deal with the apple store, and i will be returning the phone to them within 14 days if the screen has not fixed its self. Plus i also have the reception issues, very bad experience for me so far with apple unfortunately!