They has been a lot of talk about the quality of the iPhone & iPod Touch screens regarding the interlacing effect when the iPhone 3G white version is tilted or moved and is 6" to 12" away from your face.
Apple is using cheaper defected screens in the some iPhones, mostly the 16GB White iPhone 3G models and the more expensive ones that are not defected in the black 8G iPhones.
I have compaired 3 16G White iPhone 3G with 5 8GB iPhone 3G Black and all the Black models showed slight hint of lining that is perfectly within tolerance, were the Whites, failed full stop showing lining very clearly over the entire screen, these are deemed as a lower class and don't pass for high quality screens and sold on cheaper to manufactuers.
Don't buy iPhone 3G 16 if you want a high quality screen, go for 8G or better still don't buy an iPhone
I have just sent my iPhone back to Apple, and waiting for my 3rd iPhone to arive to see if they have started to stop using cheap screens.
All iPods have these interlacing effect too but are quite all right for the purpose of the device, the iPhone is a totally aimed at the screen and so is not and the black versions are ok so why put **** in white 16G and make you pay more