I tried to buy one new from Costco and have had problems with two units. Base 2017 models in silver.
First one: Terrible gap between lid and top case when closed on one side. One side was fine, the other side had a nasty/sloppy gap like the lid was bowed on one side, unacceptable. Returned it.
Second one: Something legitimately loose inside the computer, which was otherwise perfect from a quality control/cosmetic standpoint. Thought I had a real keeper until I was handling the computer normally and felt something shift. Lo and behold, something inside was moving left/right what felt like a quarter inch, and you could feel it with your hands on the bottom case. Since the computer was absolutely pristine otherwise, and since I could get an appointment at the Genius Bar the same night I received it, I broke my own rule of never service a machine that's in the return window, and I brought it in just to see if it was something simple. They opened it up and found nothing, but definitely heard and felt it. They suggested either sending it out to the repair depot for further investigation (sounds like this is a display issue from doing some searching) or returning it, so back it went.
I attempted to order a 3rd one, and Costco canceled my order, citing a limit of 2, despite returning the 2 I ordered for legitimate defects. Called them and explained, and they wouldn't budge. 2 is 2, according to them.
They said I could order another color/configuration, so I've been sitting here all week debating if I:
1) Order a base model in space gray (really don't care for anything but silver, space gray just seems so drab).
2) Order the higher spec i5/512 model in silver for $200 more than I need to spend.
3) Log in to my wife's account and order another base silver, with the threat of her needing to physically return it if there's a problem instead of me (I'm assuming this would work since her order history doesn't show my computer orders like my history does, despite us sharing a household membership? Not sure).
4) Forget it and move on with life. There aren't any new silvers anywhere else on earth from anywhere I'd feel comfortable buying from, and I've scoured the internet. I'm paranoid I'm going to get banned from Costco if I try to return a third one. I don't care if they ban me after accepting the return, but I'd hate to get banned upon trying to return, and not being able to and being stuck with a machine I am unhappy with that is defective or has poor fit and finish.
Either way, if I order a third one, that's the last one, regardless. This is exhausting, but I really want one of these little 12"ers. It's also exhausting that I have to order and wait every time, and can't just go to a store and pick one up in person. Why is it so hard sometimes to get a good product from Apple? IME, they are either perfect on the first try, or it takes 3-4 tries to get one that's finally acceptable.