Before Apple shows that this issue is resolved: www.staingate.org, any new model is just a waste of money for me.
Buyer beware!
obviously it's not definitive, but i suspect cleaning products may be to blame, or blame in a large number of cases.
edit: knock on wood.
On mine, I would just use a water-dampened, clean, soft towel if I need to clean my screen. And by clean towel, I mean clean. I don't even set it on the counter as it can pick up particulate matter. And by soft, I mean never a paper towel. Ever.