I use xournal to annotate pdfs on an N800. I have to zoom in from "pdf reading scale" to "shaky old man scribbling scale" to write legibly(*), but for purposes such as making standard copyedit notations it works acceptably for me. It isn't as pretty, or easy, as when I use my Thinkpad X61 tablet, but the tablet won't fit in my pocket.

For notetaking on the N800, I use the onscreen keyboard and the notes app. This works better for me (fewer typos) than the physical keyboard on the N810. I do use xournal on the X61 for taking notes, but I would not be able to do that acceptably on the N800.

YMMV.

* my grad students require a year of practice before they can read my block capital printing when I use pen & paper, so "legibly" may be interpreted loosely here.