E-books?

Amazon has announced that its sales of e-books has surpassed its sales of hard cover books. The idea is to settle (in their interest) whether the e-book is for real or just the latest new Coke. I'm not a luddite, but I am a late adopter. I'm not going to spend the money until I'm absolutely sure I need to spend the money. As someone who writes a blog, I surely buy into the idea that people will read what one would write on a screen. But there is a difference between the shorter posts and and the longer books. So, those of you who have a Kindle or other e-book supporting device, worth it? Pros? Cons? Have lots and lots of the paper ones, what would I gain by starting to switch over?