More on Nano screen issues...OK folks there are two issues plauging the screens on the Nano.
Firstly, they scratch easily. This should be of no surprise to anyone. It's a polycarbonate! If you put your Nano in your pocket or whatever expect it to get some minor scuffs. No big deal. In fact the plastic covering the screen is made of the same material used in all other iPods. So don't whinge.
The second issue is more significant. Some of the screens will break. Crack. Nasty. Apple are claiming that this is due to a manfacturing error and only occurs in a tiny percentage ("one tenth of one percent") of cases. The good news is that they will replace your Nano in the event that this happens to you.
Anyways, here are some articles about the screen issues...
Buyers get second bite of the Apple - Breaking - Technology - theage.com.au
Gizmodo: Apple respond to busted Nano owners
Gizmodo: Show Us Your Busted iPod
Slashdot: Apple to Replace Faulty Nano Screen
CNET: iPod Nano: Why scratch and sniffle?
Herald Sun: Problems with iPod nano
The Australian: Faulty iPods replaced free
AustralianIT: Problems with iPod nano