I got the same treatment at the Plano TX Apple store, they were nice but couldn't see the lines no matter how much I showed them. Not even when compared to the old Rev A machines for appointments with the Genius bar that interestingly enough the staff was running around with. Don't get me wrong, they were all polity and nice but could not see any lines. And trust me they were very visible on the display machines.
Otherwise I like the store and the people working there.
I have looked at close to 10 different MBAs in different stores and any machine I have seen have had the lines, with 9C90 being the better version.
Only version that doesn't have them is the version I got
when I ordered from Amazon that has the screen 9c8F which interestingly enoughy is the same model that rev A had which got me hooked on Air to start with.
I agree that you can still use the machine but if I buy a machine for $2k (SSD version) it better have a screen that is good. Dont see why anyone should accept an inferior screen since the 'lines' also makes the colors more dull.
I am so happy with the screen I got so that regardless of rev C whenever it shows up wouldn't prompt me to trade and given the price I need to make this one last for a long time.
I know several people think they will use the new battery in a rev C but since it is only in the 17" MBP so far I expect the 15" version to get it first and I also suspect there might be issues to squeeze it into the MBA at this point.
So, there was a long rambling...
If they can hopefully it can be retrofitted in rev B once my battery dies...