Just returned from "genius bar"
Light is leaking through on the left side of my new 3G iPhone (see pic), so I scheduled an appointment at my local "genius bar."
I just got back from the appointment. The "genius" said three main things. First, he acknowledged the problem with my phone. Second, he said that Apple has not yet listed the light leak on 3G iPhones as a "known problem," and so (obviously) there is no "fix." Third -- and most importantly -- he said the "geniuses" in the store were well aware of the problem (other customers have come in to complain over the past 10 days), and he claimed they have not seen a 3G iPhone that does not exhibit the defect. That is, every phone they have looked at -- their phones, replacement phones, display phones -- has the problem to some degree.
He offered to swap the phone for me, but claimed I would have some light leak on the new phone -- possibly less, possibly more. He advised me to wait until Apple fixes the problem, before swapping, especially since I have no other problems (aside from the light leak, my iPhone is perfect).
He claimed that the defect is so widespread that it's only a matter of time before Apple takes some action to correct whatever is going wrong in the manufacturing process, adding that in all likelihood iPhones in stores at the end of the year will not be leaking light on the left-hand side.
He attached a service note to the serial number of my iPhone which says he observed the light leak and offered to swap the phone but I agreed to wait until Apple recognized the problem and fixed it at the manufacturing level.