I use a microfiber cloth to cleamn my Xoom, Nexus S and iPod touch that is only used on those devices screens, nothing else.
I'd be upset if I inadvetenly scratched my gadgets trying to clean them. When I had an iPhone 3g I used to rub it on my sleeves and scratched the screen on it so I learned my lesson then.
Since then all of my devices have been scratch free by using only one, looked after cloth to clean them.
The screen on the Xoom does sure feel durable tho.