I purchased the KING ATP course as I like the fact there are video explanations, and the course had iPad support. Just so you know, iPad support means you can watch the videos, and even download them so you do not have to be online, which is good. However, you cannot answer test questions in the app, and the website will not work since it uses flash. After taking the test, I found there were several questions not covered in the material. However I did pass, but would have liked a higher score.
ATP - Multiengine Ground School & Test Prep