My experience: I got a 3G PW batch 503 with an easily noticable bleeding light on the bottom. Returned that and got a wifi 603 with light (almost) perfectly even. Unfortunately, it suddenly developed a crack on screen. I am almost a 100% sure that I didn't scratch or hit it by accident. Today I got a replacement for it with batch number 604. Too bad the lighting is not as good as the 603 one. Amazon is sending me another PW. Hopefully I have a better luck this time
PS. Isn't this about time I ask for free non-special offer? :P