Most of the times I had good experiences with the app stores and their employees, but early this week at the genius bar I encounter with my first deception. The reason of my visit was to get my iPhone 3G replaced, it had a crack in the rear plastic side, the 'genius' initial reaction was "you hit it with something", he was very rude, acting like he was going to get a comission for making me pay for a new iPhone, he was enfatic "you will have to pay for a new one"; after a couple of wasted sentences I asked for the manager, he just showed the iPhone to the manager and I was close enough to hear the manager said to him: replace it, he has the protective shield on the screen this is a customer who cares for his iPhone. The the 'genius' said to me you are lucky, my manager was in good mood, I don't know why but he authorized a replacement.
So the best thing we can do is ask for the manager and avoid useless discussions with the wrong people.
The replacement I got has another defect: silver bezel is not flushed with the plastic part, and also has marks like they were trying to pry it out, I made another appointment to get it replaced Tomorrow.
I hope that your new iPhone doesn't show these defects, and if it does don't let a 'genius' interfere in obtaining a non defective one