What are the ideal conditions where an e-reader can shine? Paperbacks are more enjoyable to read, just as portable (if not moreso), and you don't have to worry as much about them getting damaged. The only time I can think where I would choose an e-reader over a paperback is if there were a power outage late at night, I would prefer to read the lit up screen of an e-reader over reading a paperback with a flashlight.
I love reading but dislike the actual act of reading a book. I've always found books to be awkward and annoying to hold. Like, when you're reading and one side of the book is angled weird because the other side still has all the pages so you have to bend the spine or tilt you head awkwardly to see words on the inside. Plus paper dries out my fingers and I always wind up licking my fingers a lot when I read.
So having a compact little square with a screen that is perfectly flat, always easy to read, holds all my books, has a built in light, allows me to connect to social media sites (GoodReads has found me a few books to read) and I can buy books instantly from the device. It's a no-brainer. I'll opt for the e-book every time. Plus I just like technology and I find the device to be a great piece of technology.
But that's just me. I know not everyone cares about the things as much.