Just returned my MacBook Air today for a refund. Purchased it at a store on October 31 (week 43, one of the first ones to hit stores). However, I've been busy so I stupidly did not open it until last night. I'm pretty picky, and I was working in the dark, so I noticed the lines right away (in bright light, they are harder to see), but didn't think much of them until I stumbled across this link in the Apple Discussions. Once I saw this discussion and really took note of the lines, they are REALLY annoying. It's like the FedEx arrow: once you see it, you can't avoid looking at it.
Even though the return period for my MBA expired on November 14, the Apple Store in Columbia, Maryland, was amazing. The Genius working there saw the lines immediately when I loaded up Google.com, and he went to discuss the issue with his manager. Both of them were seemingly aware of the problems with the MBA screens, and did not give me a hard time at all. They immediately offered me a refund and marked my MBA as "DOA" in the computer system.
I looked at the 2 MacBook Airs (Rev 2) they had on display, and both had the issue with the lines.
Both the store manager and the Genius said they haven't heard anything about Apple fixing the problem, and just told me to wait and see what happens. They offered to give me a replacement new one, but said it would most likely have the line issue as well. They were the ones that recommend I just get a refund, and it took about 2 minutes.
So now I have to decide how long I want to wait for the issue to be fixed, since I really wanted the new MBA for traveling. Plus, I need to decide whether or not to cancel my order for the 24-inch LCD, since it can't be powered by my old MacBook Pro. SO FRUSTRATING.
To everyone who doesn't see the lines: I envy you. It's possible you got a fluke MBA, or just can't see them, but either way, lucky you. This issue definitely does exist and it affects most -- if not all -- Rev 2 MBAs (especially if Apple is telling people that's how it's supposed to be).