I belong to Audible.com, and have listened to over 260 books over the course of four years. I mostly listen to books while commuting (one hour each day), and walking for exercise. As someone pointed out, you wouldn't want to "listen" to a programming language book. I'm not sure that any audio programming books exist -- not on Audible anyway, and they have thousands of books.
Sometimes I will be become preoccupied (usually because my mind starts to wonder), and find I need to rewind. There is a handy button on the Audible.com app for my iPhone that rewinds in 30 sec increments, so that makes it easy to replay something. Frankly I find myself having to do the same thing when reading a "real" book sometimes -- I'll have read a page or two and then realize I wasn't really comprehending the material.
I like to listen to fiction, autobiographies, history, and non-fiction. I recently listened to "Getting Things Done" by David Allen. There were a few places where he referred to figures in the book. Obviously I couldn't look at those in the car (most audio books on Audible that have figures have an associated PDF that you can download).
So yes, I believe audio books increase our productivity, because you can be listening to them during what would otherwise be "dead time". I don't have to spend time reading the same books, which would take away from free time I could be spending on something else.
One disadvantage I'll point out, is that you can't look up passages if you want to refer back to the book later on. There was a recent question on the Science Fiction & Fantasy Stack Exchange site about the book "Hunger Games", which I had listened to several months ago, and I could answer it only in general terms because I couldn't look the passage up. If I had bought the book for my Kindle, I would have been able to do a search.