I've been through 3 iPhone 3G's already and I'm currently on my 4th one. I remember when I got my first 3G, I could see shadows of the inner components if I looked at the back in a very dark room. My current (4th) iPhone does not have any cracks (yet) but, it has a few chips in the plastic (which were probably my fault somewhere). The thing is... this may be different plastic or treated differently because I do not have any cracks forming on this one AT ALL and the chips haven't gotten any larger. Here's the good discovery though... If I go into a dark room and look at the back of the iPhone, I cannot see any light showing through the plastic. I don't see the shadows of the internal components on this one. Could it be that Apple is using a thicker plastic now? Those of you with cracks, check the back of your iPhone in the pitch dark and see if you can see the shadows I am talking about. Make sure you turn up your screen brightness. It also helps if you lay your iPhone face down to block light from the screen. If you don't have cracks, you should check anyway to see if what I am saying is true. I only have 1 iPhone 3G so I cannot really test this on other units. Thank you! Also, I was just at Wal-Mart and the demo model they have does not have the wavy lines on the screen... I think the QC department is kicking it up a notch on the iPhone 3G build quality. It's about time!!!