Great at your own pace

As far as features that Interact provides, Navigator is an incredibly useful tool to accompany official GMAT questions. Solutions in Navigator fit in with content in the Manhattan Prep course, and help clarify the often complex solutions found in the official books.

The quant section videos do not often delve into difficult topics, but the strategy components are most helpful. The advanced quant eBook, which is included with the course, covers useful material and additional challenging practice. I found the actual GMAT's quant section to be much easier than the quant found in Interact's practice exams.

The verbal content in Interact covers tricky rules well, and quizzes you on them. Blog posts (which can also be accessed for free) cover strategy for timing, which I used when taking my exam.