I noticed when I press firmly on the back of my macbook pro 15 late 2013 towards the middle and the macbook pro label there was this crunchy sound like the AL was pushing up against the components inside. I picked up the Pentalobe screw driver for $8 at my local computer store and carefully removed the back. There are about 10 to 15 little spring loaded grounding pins around the mother board. When I press on them you can feel and hear the springiness. Obviously there is going to be slightly more flex in the middle of the back because it is not screwed down in the middle and AL is flexible. Its pushing against the 3 pins as shown in the photo and thats what makes the noise. Other then that the computer has no creaks. Some may say they do not notice this and it is possible some springs are quieter then others or that they may break in after awhile. Also as dust builds up over time things could change too. You can't hear them if you have background noise or in the store. I just don't see a reason to exchange over this unless you have some other areas of the commuter that are creaking. The reason why they are springy in the first place is because AL is flexible and they need to be in contact with the case back at all times. I saw some posts where people where removing them but that seems crazy to me as they are there for a reason. I feel better knowing its not the back pressing against the heatsinks or components that its designed this way. Glad I got the Pentalobe as there was already some dust inside the case so I plan on cleaning it every couple of months with my Giotto rocket blower used for cleaning camera lenses etc. Do not used compressed canned air. Also remember to lay the screws out in the same order as a couple are different lengths and not to over tighten/strip them.