Not that there's any way to tell who he is, but autocruzer didn't say anything about replacing the calipers, just that only the early builds would have the weights.
I would think that if the problem could have been resolved with a simple change in pads (without sacrificing something else) GM would have certainly done that instead. Then again... lead weights are a lot cheaper than brake pads...
And yes, this is undoubtedly a fix for a noise problem. There's lots of ways it can be explained but here's the simplest I can think of...
For anyone that's been into car stereos forever Dynamat used to have a little product demo that was very simple. They had two clerk / desk bells (like you used to find in hotels), one rang just as expected but the other had a small nickel sized piece of Dynamat stuck on the bell and it would not ring. It absorbed the resonance / vibration.
I hope they come up with a better solution for those that get the weights though. If I windup with one with weights I certainly wont be worried about it for quite a while but I would certainly expect them to correct it in a better manner.
