I have a Kindle and love it, however, it does not allow you to download the free e-pub books that many local libraries are now offering. You have to buy your books from Amazon. Many are free and reduced prices, but free would be better! There is a program out there to allow you to convert e-pub books to the kindle format, but I can only get it to work on classic books that are out of copyright. I also don't like the battery replacement with the Kindle.
If I were to purchase a new one, I would purchase a Nook, or another brand that allows you to download the e-pub books. As soon as my Kindle "dies", I will get a Nook.
I didn't like the iPad because it doesn't seem to have the "electronic ink" that e-readers have so that it is easy on the eyes. Just my thoughts - hope it helps!