My boyfriend got me a kindle for Valentine's Day a few years ago, and I love it to pieces. I take it everywhere with me and always have a variety of books to choose from.
On the other hand, I still love actual paper books. I love to smell them (I'm not weird, you guys know what I mean, right?) and hold them. And I love to read in the bathtub, which isn't really practical with an eReader.
Having said all that, when I find a book that I want to buy the main deciding factor is usually price. If I can get a paperback copy at the used bookstore for $1.50, I'm getting it. But if the Kindle edition is free, I'm going to get that one.
So in terms of buying books from the site, it would really just depend on the price. I would be more likely to get the digital editions of they were cheaper than the paper copies.