I live in Scottsdale, Arizona U.S.A.. I know of seven rev B MBAs here that do NOT have any lines. I have seen the lines in the Apple Store where a rev B MBA owner's had lines (which were hard to see except on white background and at very bottom of display), but more importantly had uneven backlighting. I think it had been dropped as was a dent in it.
I have read many others that say it's on every single rev B MBA. I find it hard to believe. Mine has no lines, and I know several others who own line free rev B MBAs. So, I have wondered if maybe has something to do with climate??? Why is it there are so many line-free MBAs here? Just a thought...
FWIW, I read another thread that has seven postings of people that, like me, claim to have a line-free rev B MBA. So, either we are all blind, or there are a bunch of MBAs out there without the lines. I think the lines must be happening to a small percentage of the MBAs, but I wonder what the differences are. People that have line-free rev B MBAs have bought them from release date through a few weeks ago. There are two models of displays, and both have line-free so people claim.
I would say, buy it from Apple. Open in the store. If ANY problems or lines, demand a different new boxed MBA. One other caveat, I would advise you not to say anything to the associate before buying and opening yourself in the store. I wasn't concerned when I bought mine, as I had already seen a bunch of line-free MBAs and it was not that I thought there would be even a 5% chance that mine would have lines. But, if you are really concerned, I think opening in the store as soon as they have given it to you and you paid, is the best way to ensure you get a line-free rev B MBA. You are going to be paying a lot of money, and Apple is NOT going to be unfair to you. If you have lines, they will replace it. I have had a personal experience of being concerned about something else, one time, and the sales person told me not to buy if I was concerned... I did buy and it didn't have any problems (different computer/different issue). I have read it from many on this forum that they kept opening boxes until got one with no lines or very faint lines that could see only on certain white background web pages and such. I think you will be better off to go in with a positive attitude and assume you will get a brand new line-free rev B MBA... that is more likely to be the best way to deal with Apple if yours ends up having lines. Be cautious but don't assume the worst just because some others have posted their line issues.
I personally wonder about the dry climate here and if that is why they're line free. However, it could be where they are shipped from, the model you buy (as far as low-end or high-end), where you buy, and how has been cared for (like I said, the one I saw had a dent like definitely had been dropped)???
I really don't understand how many as a percentage of rev B MBAs have these lines??? It just seems really odd to me of how many I have seen without lines. I know people seem to only report when there is a complaint, and that may be why there are so many people here who have posted the line problem issues.
Best wishes in getting a line-free rev B MBA. It is one amazing computer in all aspects from speed to portability to power and capabilities.
Cheers.