I have a bad habit of skipping ahead when reading fiction, and the sequential nature of ebook reading helps prevent me from doing that.
For technical literature it's not so good - I still print PDFs of scientific papers to take home with me. I'm reading one book that is too long to print, so I'm struggling with the .pdf on my n800. Not fun. A large-screen color device with a good quick .pdf and .html reader would be perfect for scientific articles, though.