Sorry to hear about your MBA.
However, I have not heard about this grey lines thing. And I'm a bit concerned because I'm trying to decide between a MBA (waiting for rev. C) or MB (Al unibody). And I've just heard that UMB got updated with the same screen as MBA ones.
So, will this both have the grey lines thing? Which is the incidence of such defect?
The screen issue is one that I am familiar with as mine does exhibit the behavior (or my eyes/brain believes it does) from time to time under the right conditions. It is a bit annoying (esp. given what apple charges for these things), but I really do enjoy using this machine vs. the other alternatives in the Mac lineup. There are some theories that it is caused by undervolting the panel (which might mean the panel models -- 9C90 and 9C9A -- that exhibit this behavior on the MBAs would function perfectly on the MBs assuming they have more spare juice and that they have found a panel that works more reliably on the MBAs as some have had good luck with the 9C8F variant, iirc).
I think it's a good thing that Apple has decided to update the panels on the MacBooks. The problem is even with some examples of that in the pipeline, there is no guarantee that all new MBs will be made this or that when you go and buy one you will end up with one with the screen (think of the scope of their operation and inventory, etc).
I cannot speak to the incidence. You can look back through the history in this forum, which is not a scientifically significant nor likely representative sample of Apple's customers (the people tend to be more savvy and either more embittered or smitten
). In some people's experience it has been quite high. Others have seen only perfect MBAs everywhere they look.