If you have an Apple store near you, just call them and set up an appointment and they can replace the LCD panel.
Before I ordered my custom 27" iMac, I went to the Apple Store and asked if I could return to the store if the display was defective or had a dead pixel. They said that they couldn't return a online ordered custom system at the store, but they could replace the LCD panel if there were any issues.
I had a few screen issues (dead pixels, yellowing) with the first couple iMacs that I got. So when I went in to get my 3rd iMac I asked them to open it up before I take it home. It didn't have any of the previous issues, but it did have a similar band. The tech told me that it was normal and would go away over time (so I decided to give it a chance). I've had it for over a month now and so far so good. I think it has gradually disappeared and I don't really notice it now.
So I would give it a few weeks before you send it back. For me the only real show stoppers are the dead pixels and yellowing...
I bought mine in May and had to bring it in 3 times for them to replace the screen. The 4th time they ordered me a new one, and it still has the same problem... I've given up for now...
Isn't there something we can do to get some sort of resolution to this problem, other than going to the Apple Store? Maybe a more direct connection to Apple itself... Will they ever recognize that this is a recurring problem?
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So you had it replaced all 4 times for the same problem (shadow along the bottom)? Did any of them seem better than the others and do you regret not hanging on to one of the earlier ones?