I don't have the N7 myself, but I have been following Swedsih fourm discussions about it closely (because I've been thinking about getting one).
Screen lift has been a big issue, especially with the early batches. It semmed like a very high percentage of buyers had some degree of screen lift.
I have heard about one or two cracked screens. Probably in connection with screen lift. I think bot (or was it just one?) had screen lift prior to getting a crack across the screen.