I have a kindle and I like it for a few reasons -
Amazon is a powerhouse of books and book deals, everything just works.
I have a backlight so I can read at night and not wake up the wife
I can rent books from the library on my kindle
Large screen size seems like a downside to me, I take it for travel a lot and I have several pairs of pants where I can slip the kindle into a pocket (it's not pretty but it works).
Oh, and I don't have the will power to read on a phone or tablet. There's too many other things that are way quicker and more immediately ingestible. If I'm going to read I have to have the separate device that can't do anything else - which is why I never got one of the google e-readers, it just became a device I tried to install android on.