Bought a white 16GB on launch day at an Apple Store in Paris, France, which had no defects. After playtesting it for a few weeks (I love it...) I decided to buy one for my wife as well, to upgrade her from the iPhone 4. Tried Apple's online reservation form every day last week (for in-store pickup) and finally yesteday I was allocated a phone.
Went to pick it up today and opened the box in-store (again, Apple Store Paris, again, a white 16 GB). It had a very light scratch on the back -- very superficial but about about 3/4 inch long, and one of the white antenna joints was not completely white -- looked like it had glue smudged across it or something like that. I hesitated for a moment but when I pointed out the defects to the salesperson he agreed it was not normal and agreed to see if there was another one he could give me (stocks being limited and the store having guaranteed a certain number of each model to the people who reserved online). He said if not of course I could return it for an instant refund to my credit card.
After about 5-10 minutes waiting, he came back with another new phone. He was very friendly about it -- he said their goal is to make me happy. He processed a return on the spot and we opened the other brand-new box. This one did not have any obvious defects and I am glad I made the switch (if you examine it VERY, VERY closely there are two really minuscule nicks in the silver chamfered edge at different spots, but really the size of tiny dust particles -- which I am willing to accept -- I know that with normal use it will get a lot more of those).
While I was waiting for the replacement phone, I saw another person buy and reject a phone because of physical defects -- also a white model. Didn't see that phone up close though.
Clearly, Apple have gone with an inherently more fragile design this time around. Whether at the factory (which I agree is unacceptable) or in normal use (which is practically inevitable unless you totally baby your phone and cover up its beauty in a case), clearly this phone's design makes it more fragile to nicks, scuffs and scratches. But I still far prefer it overall to the 4/4S design. It truly is the best user experience yet in an iPhone.
Yes, the shiny chamfered edge is beautiful -- but it is also fragile! I always resell my previous phones on eBay and get pretty good money for them because they are in excellent condition. It will be harder to keep the iPhone 5 pristine, so yes, I will probably lose a bit of money in 2 years when I upgrade to the iPhone 6 or whatever.
If you are a potential buyer worried about out-of-the-box defects, Foxconn's tightening of QC will probably mean virtually no more defective phones will be getting to consumers within another couple of weeks. So if you cannot inspect where you buy knowing you can swap immediately, then I'd say wait a bit. If you are really worried about overall fragility, then I'd stay go with/stick with a 4S and wait to see what the 5S/6 are made of. They might engineer the aluminum differently, or maybe the coloring/polishing processes, or maybe even go back to a stainless steel antenna. But then again, maybe they won't! So if you want one of these more fragile beauties, go for it! You just might have to be cool about potential wear & tear.