I didn't imagine the thread was about Kindles versus hardback books. I assumed what was wanted was pros and cons of Kindle versus other ebook readers.
That said, I don't have any cons. All ebook readers have the same issues with formats, DRM, and books with photos and illustrations.
I want my ebook reader for, gasp, reading books and not for browsing the internet, doing email, playing games, watching movies, listening to music, or running inumerable apps. I also have valid reasons for not wanted an ebook reader that does all those things, mostly related to battery use. No, if I wanted all those things I'd get a toy from Apple.