Pretty much guaranteed path to a great score.

Strengths:

The course content is thorough, well explained, and comprehensive. The interface is really easy and pleasing to use--completing lessons and practice problems gives you a little dopamine rush. The practice and review tests are great, and the ability to create custom practice tests is invaluable.

Would make the product better:

Firstly, it's a colossal amount of content. I realize this is a feature, but it's hard for me to comprehend how someone could get through the course in four months. I did the six month course while not working full time and I still didn't finish it in the allotted time. Secondly, I wish the IR section had more questions or even practice tests. Despite having a good grasp of quant, I was frequently stymied by IR questions and didn't know how to practice and improve. Finally, there are some sections with attempts at humor that didn't click with me.

If you want a great score on the GMAT, TTP is a clear path to get there. I started studying with a solid grasp on verbal but really shaky quant skills. TTP's thorough, methodical process got me to a point where I felt really confident answering quant questions, and ultimately I scored higher on quant than verbal. For both quant and verbal, TTP does a great job of teaching you not just the topic, but also how to approach questions and eliminate wrong answers. By the time I was taking my practice tests, I was scoring highly and feeling confident in my knowledge. On test day I got surprisingly psyched out by the experience, but even while feeling really nervous and like I was doing poorly, I was still able to keep my eyes on the prize, keep moving, and secure a 760.

Even if you're already using some other prep materials, I'd highly recommend the $1 trial so you can experience the custom practice tests with clear, detailed explanations. I found myself really missing these explanations when taking the official practice tests or using questions from other sources.