I'm paranoid about damaging any expensive phone screen, because you can't easily/cheaply replace it. So I had already ordered some N900 screen protectors BEFORE I'd even ordered my N900 from amazon! Needless to say, I've had the beast for 5 months, and the screen protector shows many small, light scratches and a couple of heavier ones. All that makes me think is, (apart from time to change the protector) those very same scratches might well be on the actual screen itself if it wasn't for the protector. I take care of my phone, don't work in construction, but those scratches still managed to appear.

Also, for those of you having problems putting them on, I followed instructions for an iPhone screen protector on YouTube, using a credit card - works like a charm. No water (yikes!) necessary!