The other day I concluded Kindle rocks, after having received one as a present. So now, having flown for a cumulative 15 hours, I can tell you it really rocks. This is the perfect "book" to take on an airplane. It is small, light, easy to read, and of course the equivalent of 200 books when fully loaded, so you have a ton of content. The battery life is excellent, especially with the "whispernet" turned off (which of course you must do on an airplane anyway). Pleasingly the flight crews treat it like a book, not an electronic device, so you can use it during takeoffs and landings and while taxiing (actually I think they didn't know what to make of it; YMMV).
I found myself continuing to look up a lot of words in the dictionary - that's an unexpectedly useful feature - and also switching between books some; I found myself reading The God Delusion and The Black Swan more or less interleaved, for some reason. The reading experience is really good, you do "disappear" into the experience, as intended. I have not yet gotten used to the big next page button on the right, however, it is convenient, but a little too convenient, it is too easy to push when you don't mean to. At this point I doubt I'll get used to that, it is just a not-perfect implementation that you would think might have been exposed during beta-testing, and will no doubt be addressed in version two. Another not-perfect thing is the "back" button because it is not matched with a "forward" button. Sometimes I hit "back" when I meant "previous page", but when I did there was no "forward" to easily recover. Another thing for the next version. But these are quibbles because otherwise I like it a lot.
As you might expect it is a bit of a conversation starter; people see you reading, and either know what a Kindle is and want to see it, or don't know what a Kindle is and want to see it. I may have sold a few en route :)
Now that I'm in my hotel, it still rocks, because I can go to bed and read easily; the smallness and lightness and easy-to-read-ness are all still important, as is the fact that I have all this content from which to choose. Awesome, I love it.