Holistic and high-level learning experience

Strengths:

The program offers an in-depth review of everything that could possibly appear in the GMAT. One of the biggest strengths is that the program has SO MANY exercises to practice, and the program pushes you to practice every topic so many times that in the end you become advanced in that topic. The Verbal learning experience is very good for non-native English speakers like me.
Additionally, the program includes several tools that I found very useful: the error tracker, the "must know" cards, and the detailed explanations of every single question.
Some bonus tools that I liked in the program are the video of the day and the strategy lessons. These were definitely very helpful to prepare mentally for the test.

Would make the product better:

The program is longer than I expected. I had to invest several additional months in my preparation. In the end it was worth it, but be prepared to put in many many hours, especially if you come from a non-English speaking country or from a country that does not normally offer top Math education in high school (this was my case).

Overall TTP is an excellent program for people looking to improve their score or to achieve a high (or very high) GMAT score. The program let's you choose your target score range and it creates an ideal study plan for you. You literally just have to sit down and do what it recommends. The program goes into as much detail as you want and it has several features that will help you in your preparation. The program requires heavy time investment from yourself, but hey this is the GMAT and it is not an easy process!
TTP is definitely a better program than other programs I tried in the past (tried two programs a couple years ago), so I recommend TTP all the way.