I looked into this myself. I found some tests that one person had done, where he tried really hard to get as good using his finger as he could with the stylus. In the end he posted pix of text written by both finger and stylus - you could not tell the difference! Now, I've tried this and its really hard to get "fine" text with just your finger, but I havent really practiced it.
I can say that I was unable to find any stylus that people didnt report "scratches the screen". Some people said the scratches were so fine and hard to notice you had to get the tablet out in the sun light and have it powered off to see them. Myself, I have a bit of OCD when it comes to my devices and hate to have even the smallest flaw (yup, I am often miserable in case you were wondering!
) so I decided I would never use one on my N10.
A good way to find the names of the stylus' that people were giving good reviews was by looking in the comments of the "note taking" apps.
If you end up getting one I'd like to hear how you like it...