This is a slippery slope, and I've been down it before. My iPad 2 (like the 2011 model, not the Air 2) had a LOT of dust under the screen right out of the box. This was back when they had a month lead time on them because EVERYONE was ordering them, so I'm assuming the manufacturing was going at breakneck speed at the time. I returned it, and the second one I got developed the same problem over the space of about two weeks. My next one had three dead pixels. My original iPad 3 (or "New iPad") had what looked like some kind of water marks or stains under the screen. I returned it, and ended up with a unit that had a scratch on the bezel. The scratch was small and unnoticeable, but still irritating. I had the same types of issues with a few iPhone 4's as well. It was during around the same time as the iPad problems I was having, and I almost completely gave up on EVER getting an Apple product that was in good shape out of the box.
I felt bad returning things over and over, and at one point I was starting to get the feeling I had worn out my welcome at the Genius Bar. They were getting really tired of dealing with my issues, and honestly, I was getting so preoccupied with any little defect I could find, it was getting harder and harder for them to even figure out what I was complaining about. As someone else mentioned, it's hard to show them cosmetic problems in the Apple Store because of the way the lighting is set up.
I was really getting concerned about their hardware quality control though, and almost gave up on Apple completely. But my iPhone 5 and every other Apple device I've gotten since then have all been more or less perfect. Every mass produced gadget you buy will have little imperfections here and there, and I'm really good at finding them. I know exactly which lights in my house will expose them the best and I will find things most normal humans wouldn't care about. But the thing is, I just don't care anymore. I don't want my gadgets to control my life. There are other, more important things to worry about.