Hi!
I'm just like you - one of those people who happens to noice every single little cosmetic defect, and sometimes it can drive me insane.
with that said, I have good and bad news for you:
the good news is that apple has an awesome return policy so if you decide to replace it you can, more than once even.
the bad news is that these are mass produced items, every single one of them will have some kind of defect somewhere, so you won't get you perfect device. those who say otherwise are just blissfully ignorant.
with that in mind- I'd recommend you set yourself the bar for what is considered "unforgivable" - for me it is screen damage and things that are large enough that I see them during my everyday use of the device.
don't forget to update on your decision and outcome, good luck!