So, after quite the hassle, I received my replacement N4 and it has the same issue as the first.

(I can't figure out how to insert the full size image, so you have to click the image.) The dark bands aren't noticeable under the black notification bar, but if I try to read a book fullscreen with the kindle app, or use a screen test app like this one:
I see this banding, as if the screen isn't lit correctly at the top. It is quite annoying. I'd sure like to know how many of the rest of you have this issue.

For general interest about shipping and replacement times, here is some info from my experience:
Ordered Jan 29 (first day they reappeared in the Play store)
Shipped Jan 31
Received Feb 1
Called Google support Feb 8 and described my issue
Was told this was not covered under warranty, and replacement would be at my own risk -- if I returned the phone and they found nothing wrong with it, I would be charged the 15% restocking fee and have to pay full price for a replacement.
Replied by email Feb 8 and sent photos. Received an RMA for return.
Sent another complaint on Feb 9.
Received email Feb 10 offering a warranty replacement.
Thought it over for a few days, but on Feb 14, emailed to accept the offer.
Received email changing the return RMA to a warranty replacement RMA on Feb 16.
Replacement N4 arrived today, Feb 20.
Powered on, loaded apps. When kindle app was installed, downloaded a book and opened it.
Same issue as the first.

So, I guess I'm keeping the original phone. I can live with this annoyance, but it's not the kind of quality I was hoping for or expecting for $400.

Opinion? should I return the replacement phone, or just keep it and sell it on eBay? Now I'm afraid that when I return the replacement, that I'll be charged.