It's not even the lines as such that are disturbing; it's that they become wider and narrower as text scrolls across the (landscape) display. It's a beautiful effect if you try to create it, but somewhat irritating when you just want to read a web page. (I refer to web pages as it needs a white background and black letters for this effect to become visible; the grey UI of the N9 does a good job in hiding it in most other applications.)

I will take the device to a Nokia care point next week and see what they have to say about it. I'd hate it if they'd come up with "this is normal on these displays". It's actually not acceptable on a €700-device.