I read ebooks on 2 devices: an Ebookwise and also my Dell Axim X30. I LOVE them! I will only read a paper book now if it happens to be in the house and I'm out of reading material for either of my readers.... not likely to happen LOL!
As for reference reading. I LOVE the Ebookwise for that. I'm currently reading a book on grassroots marketing for my business. With the Ebookwise I'm highlighting and inserting pages for note taking. Then when I'm done, I can go back and just read what I've highlighted and my notes!