Just a note to add to this thread. I've had a Kindle 2 for close to a year and love it. However, when I learned that I could use the Free Library of Philadelphia (I live in the rural South and couldn't find a library with ebooks that I could access), I bought a Sony 350 (about a month ago). I'm using it only for library books.
My only disappointment with the Sony was the limited font sizes. There's no way that I can read the small and the medium wasn't really what I wanted either. But, when I change the page to "no margins" or whatever it is, I am happy. I'm not swearing that the font is larger, but it certainly seems so. If I read on the "large" size, I would wear my thumb or finger out with swiping so often.