I don’t have either, but I ran across this comparison on the devices. It says get both, if you’re a consumer of media and culture. To some extent I do think that it’s got a perspective that makes sense, and if you can afford a $500 iPad (or more), then you can probably add in a $140 Kindle without worrying about it.
I had a Gen 1 Kindle, and I have an iPhone that is my primary way to read. I read on flights, and while I do take breaks and play some games, I think it’s a matter of attention span. Books that are really, really good hold my attention, and I won’t move on to anything else.
Books that I struggle with, or require more thinking, I switch off at times. When I read business books, I sometimes need to think about something, so I’ll close the Kindle app for a minute, maybe play a game, and let my mind wander with what I’ve read.
There definitely is a difference in reading on an LCD and e-ink. It doesn’t bother me, or it doesn’t appear to, but I understand that it might bother some people, and if that’s the case, a Kindle/Nook/eReader makes more sense.
I’m not sure if I’ll get an iPad. It has to function in my life and add something to it, and I’m not sure it’s that much better than an iPhone. Talking with someone recently that carries an iPhone, iPad, and laptop, they tended to use the iPad regularly, but it didn’t remove the need for the other devices. We’ll see if I make a case in my mind to get one.
However you do it, go read. It’s good for you.