Every week I drive across the Big Island, a distance of 86 miles each way. Audiobooks, which I'd never bothered with much before, turn out to be a very enjoyable way of dealing with the ride. There are two major disadvantages: "listening while driving" is not suited for deep attention and "listening while sitting on the couch staring blankly" is not appealing in the evening.
Amazon/Audible's new "Whispersync" feature goes a long way towards addressing these. It's an "it just works" feature that means that after listening to the audiobook (perhaps only with the Audible app) in your car, when you open the book with your Kindle (I've tested it with my Kindle hardware, with Kindle for Mac, and with Kindle for iPad) you get a message saying, e.g., "The furthest read page was 92 from iPhone 4S at 9:51. Go to that location?" And vice versa: when you open the Audible app post-Kindle you have the opportunity to move forward.
It seems to take no more than a few minutes for the updates to move through the cloud and you don't have to buy the book and the audiobook at the same time. (I mention that because I happen to have one book that I started with the audiobook, decided that I was too interested in getting through it to take it in 1.5 hour stretches in the car, and started reading it on the Kindle, and all of a sudden, it's Whispersynching.)
The downside is cost: You have to buy both the Kindle book and the Audible audiobook. Audible books are ridiculously expensive if you buy them one-off: \\(20+. Subscription prices can drive that down to \\)10 per book, but only if you commit to two books per month, which is a lot of listening. But not, for me, a lot of reading.
At the moment, Amazon is offering Whispersync-enabled audiobooks for \$3.95 or less, which is a great deal and just about the perfect amount to entice me into "Oh sure, maybe I'll listen to that in the car." on all my fiction purchases. On the other hand, it destroys the value proposition of an Audible subscription, and I'm under the impression Audible is successful enough that Amazon is unlikely to want to gut it (yet). So my guess is that the low price of audiobooks is to introduce the feature. So snap them up while you can.