I think the P90x is a great fitness program for people who are in decent shape. I do not think this program is the right choice for somebody just starting out as there are some impacts to the lower and upper body. If you stick to the fitness program you will get in better shape.
P90X is a good fitness program for some people and not for others. I think that each progrma that is written for fitness is going to be different for each person who uses it. I think that if you like this type of workout it will work for you otherwise it will not.
While it's not going to build muscle like they show on the TV ads. It will keep people entertained and exercising over the term they decide to exercise for. Having a routine that changes speed and intensity does help raise the heart rate to effective levels and works well as a cardio program.
I believe P90X is a good fitness program. With that said, it's certainly not for everyone. The program is highly aerobic and pretty intensive. The program, in my opinion, is best for people who want to focus mainly on fitness, rather than other adventures. It's not for the typical American.