2. Downloading free samples. I love this feature so much(provided, of course, that the sample they allow you to download is worth a damn- they aren't always, but this is a list of praise, not discord) I go through and download samples of books that I intend to buy in paper- or hardback, too, because this has actually saved me money when the sample chapter(s) have not been at all what I was expecting from reading the synopsis or reader reviews.
3. I can be reading anything, horror, comedy, gay erotica, while sitting out in public and it is going to be near impossible for someone to see the title of what I am reading, and use that to try and open up a discussion about the book. If I am sitting somewhere reading, it's because I want to be sitting there reading, not talking about the book I could be reading if Mr./Ms. Chatterbox would only shut the hell up.
*Bonus- Some of my favourite authors have started publishing novellas via Kindle only, so it's nice to have some way to read them.