commy-superman,
I like Osmosis for the fact that it's a great review. I listened to it in my walkman when I was on the subway, bus, and walking to school. As I wrote, it's great as a review but it should not be fully supplemented as an MCAT prep. There are some errata on it posted on the EK forum.
Osmosis is 12 CDs. I think the real cost is about $300 (check it on Amazon), but I got it for less than that on Ebay.
To study for the MCAT: you should use prep books like EK in conjunction with AAMC practice tests (your textbooks can be optional). I found my textbooks to be useful when I wanted more details about a certain topic. The key: practice and getting a feel of the timing.