I have not taken the MCAT yet, but I am using Kaplan for most of my preparation. I feel that there is a lot of information that would be nice to have in it, but it should be a great way to study for the MCAT. There have been people who scored 90+ percentile (even 99+) using Kaplan as their primary source. There are terms that I feel should have been included in the Behavioral Science book, and some things could have been explained in more detail in others. For example, EK (at least 7th edition) biology discusses the Golgi apparatus in more detail by briefly discussing the cis and trans Golgi and is slightly more specific when it describes how proteins are sorted for delivery to target membranes within the cell. Now, it isn't necessarily high-yield to know every detail of vesicular transport, but it can certainly help. MCAT passages can provide what you need to know about SNARES, for example, but it may seem confusing if you haven't learned about them before. Knowing what the passage talks about helps keep things straight as you read each paragraph and visualize how certain molecules move or what happens if you replace a surface residue of a key enzyme with a different one.
In addition to Kaplan, I am using TPR and some EK stuff just to cover all bases. I primarily read from my Kaplan books and only look up things in Google, textbooks, and the other prep books for more details if I feel that I don't understand something properly.
