You might think the best thing about the kindle is the near instant ability to get new books. I will freely admit that it is wonderful to finish a book and be able to click on Amazon (assuming the internet is working) and get the sequel without having to drive to a bookstore (if there is such a thing near you) or waiting weeks for the Amazon box to show up in the mail. Getting books in minutes instead of weeks is is GREAT, but it isn't the best thing.
My husband thinks the best thing about the kindle is his ability to surprise me with new books anytime, even when he isn't home, as long as he has access to Amazon. I LOVE fact that my husband understand and supports my literary addiction. That's one of the reasons I married him, he spoils me rotten. Admit it you are jealous and wish you had found him first, sorry he is mine and I'm not sharing him. Or the kindle. But it's not the best thing about the kindle.
So what is the best thing about my kindle? It is one little feature that is really on Amazon not the kindle itself. If I try to buy a book I have already bought in kindle format, Amazon warns me and reminds me when I bought it. If you don't think that is awesome you have obviously never gone book shopping with kids, quickly grabbed a likely book by a favorite author and realized hours later, half way through chapter one, that it was a book you already owned, just with new cover art. Deja vu in a really sucky way.
When I was cleaning out my bookshelves before we moved out Frankfurt I sorted my books by author and suddenly realized how many duplicate titles were in my library. I had at least a couple dozen titles for which I had two (or more) books. Yes, some books I had three copies of, and I think I had four copies of Dragon Singer by Anne McCaffrey. I blame Dakota for at least a few of those doubles because we have similar taste in Sci Fi/Fantasy books, but most were my mistakes. Do you know how much money a couple dozen books adds up to? I could have spent that money on books I didn't already have. So you see the BEST thing about my kindle is never accidentally buying the same book two (or three) times.