I only did the full length tests they offered from the prep book, but here's what I think:
Lets go section by section,
Physical Science: Too hard, too much physics, too much details. But it will let you know what topics are your weaknesses due to its detail oriented style.
Verbal: Difficulty is probably pretty close to the actual MCAT. It is quite hard. It has slightly more detail oriented questions than the "overall message" kinda question you see on the actual test.
Biological Science: Same comment with the PS.
Psychology and Sociology: Not enough Sociology. Getting a good score on this section doesn't mean you know the materials. It doesn't tell you much about your performance.
Hope this helps.