Not super easy, but they do scratch some. I have had one on my E71 for years and it only has some minor surface scratches that you can only see if the light is at just the right angle.

The one I have on my 5800 has some scuffs from the stylus, but my SO has been using it heavily since I picked it up last Aprilish.

The one on my N810 has the worst scratch of all. Somehow I managed to dig through the surface layer with the corner of my fingernail and get a really good scratch in it. Even that one isn't too terribly obvious, although you can feel it. That's the only major scratch it's gotten in the last 3ish years.

FWIW, I got the N900 protector in yesterday, and I think it's great. It has cutouts for both the prox sensor and the earpiece, but otherwise covers the entire face of the device. It went on relatively easily, is perfectly clear, and hardly has any effect on the sensitivity of the screen. I say hardly not because I've noticed any change, but because I still can't believe there isn't some effect from it.

Lastly, the texture is just the same as the original screen, or close enough for me not to notice the difference. They're both smooth, but not too smooth. It's ever so slightly stickier than the original, but as I recall, the bare screen was a little bit sticky for the first couple of days, too.