Just took the MCI after using Sheppard Air and got 100%. I did a few hours over four nights...10 hours total of studying (only because I actually read a lot of the explanations for my own knowledge). You can easily pass the test using their prep material in 5 or 6 hours. I haven't flown GA in 19 years but their prep makes it easy. I plan to use them when I take my ATP written in a few months. Highly recommend the SA boys.