If everything else about it is fine, then deciding to keep it could be much less hassle than returning and so on. I had a similar issue, and I decided it was minor enough to correct with:
http://www.radtech.us/Products/Wildeepz.aspx
I've never noticed any gap since, and while I now have six small rubbery dots around my screen it turns out that I don't notice them either.
It's possible that returning it could have given me a flawless machine, but it's also possible that I a new machine could have had a dead pixel or two which I consider harder to ignore.
DG