There is some difference for me, but the difference is skewed in the direction of classic works of literature because they are free on the Kindle. So the Kindle has had the devastating effect of making it easier for me to read the canon of western literature that I always found excuses to avoid or ignore.
Would you chime in with any favorites that you've specifically read for free on Kindle? (Anyone's contributions would be welcome). I must confess that my eye for the wonderful work of Project Gutenberg is bigger than my stomach, as I've yet to tackle the great Russian books I'm sitting on. My favorite Project Gutenberg read so far has been The Memoirs of Ulysses S. Grant and re-reading Twain for the first time since high school.
Edith Wharton. Sir Arthur Conan Doyle. Gustave Flaubert. Sinclair Lewis. Thomas Hardy. George Eliot. Anthony Trollope. Kate Chopin. G.K. Chesterton. Henrik Ibsen. Theodore Dreiser. Henry Fielding. Virginia Woolf.
These are all writers whose works I've largely left unexplored until the Kindle. I've read one or two novels from some of the authors listed above. Others I hadn't read at all. My book club is currently reading Crime and Punishment. I had read it years, probably decades, ago. I remembered very little about it, and my paperback copy was long gone, the victim of a move or a loan to a friend or God knows what else. It was free on the Kindle, as are the rest of Dostoyevsky's works.
I realize that there are arguments for and against the Kindle. But look: the canon of western civilization is free. If you have a Kindle, you might as well take advantage of it. I have, and I'm delighted.