Don't listen to the people who're saying it's not worth it. For $60, it could very well be worth it depending on how you apply it, as with everything else in your MCAT studying. If you have to drive anywhere ever, which do you think is more beneficial, listening to your Britney Spears or listening to MCAT material. If you ever walk around a lot with your iPod, again, Britney Spears or MCAT?
Even if you do listen to it, you have to do a lot more than listen, and even a lot more than pay close attention. To get the most out of audio osmosis, use it as a study guide where you study in your head as you listen. So do not use it as a first step, use it after you've studied the associated material, and use the pause and rewind buttons a lot. I would tortuously listen through audio osmosis not because the mp3's were long, but because I frequently paused and thought through the concepts being discussed in my head. I'd jot down quick notes on my hand or a piece of paper about anything that I was wondering. I just thought MCAT for a long time I guess.