It's funny because after using any of the iPod 'killers', it becomes apparent none of them could kill a fly.
emailia: yes, when the nano first came out, several were reported to have cracked. usually this was due to people having them in their little jeans pocket (the one at the front designed for change, I think), and sitting down. The nano is a very small thing, and made out of plastic, so that sort of force on it as your legs bend is bound to crack it. I've had mine for over two and a half years now and it still works perfectly well (touch wood).
missjef: it may be wise to hold off for another month; there are some rumours that apple may go back to the old iPod mini design and make the nano case out of aluminium.