I've got Kindle software installed just about everywhere now--on the iPad, on my phone, on two laptops. Heck, I've even got an actual Kindle. Now that I've been kindled for about a year, what's the result?
1. I use it for books I wouldn't normally keep. I've yet to think of Kindle e-books as mine--since, strictly speaking, they aren't mine at all, just a lease that permits me to access them. Ergo, my Kindle purchases have been almost entirely of the "read it and toss it on the free books table" variety: genre anthologies, detective fiction, etc. The obvious downside is that students are no longer inheriting random anthologies involving zombies or the latest Charles Todd mystery.
2. It's more convenient for hefty texts. It's far easier for me to lug around the latest Datlow/Dozois/etc. genre anthology on, say, the iPad than it would be for me to pack one of those monsters in the flesh (er, the paper). Presumably, a Norton Anthology would be less liable to cause permanent bodily harm in e-book form.
3. It has yet to be worth investing in monographs on Kindle. Sure, there are some recent instances of academic e-books (e.g., from Continuum, or what used to be Continuum) retailing at $14.95, and I just saw a book of interest for $9.99. But...$60+ for a book that I won't own? And that I can probably get at half the price if I just wait around for a secondhand seller? Whatever for?
4. Search vs. browsing. On the one hand, the search function is helpful, especially when I'm trying to write a blog post. On the other, casual browsing around in the text feels far more difficult. (In general, I don't find that e-books affect my actual reading speed.)
5. My hardcopies don't run out of power. Requires no explanation.