Never thought I'd go e-reader until I got one on a 3 week trip and man was it amazing. I read quick, and on an 8 hour flight plus several hours of airport hang-about, I'm done with whatever book I bring before I ever finish getting where I'm going. And there's only so many books I can bring; even 3 books takes up a surprisingly large amount of space. Got a Kindle though, and it was so small and light; plus, if I wanted a book it was like 3-8 bucks and boom, in my lap. If it's 11pm and I want to start something new, I've got it (as long as there's wifi). I still get physical books every once in a while, but only from second-hand stores.
I've got a friend who only uses his kindle for trips - the rest of the time he reads books from the library. He'll get 3 at a time, read them, and go back. Saves him money. I never have the time to do that though, so the instant appeal of e-readers is pretty great for me, even though I miss the smell of books and the impressive nature of looking at a physical collection. It's like:
"Look at that bookshelf. Damn, that's like 200 books. How cool; I could spend a month in here." vs "What? Oh, you want me to see your e-books? You mean that little tablet thing? Yeah, oh wow, 200 books on it. That must have been a lot of money."