I am on Day 16 of P90X, and absolutely love it.
You will find that the workouts are very efficient and don't waste your time. You are constantly moving and the DVDs which I thought would get monotonous and boring, are actually quite engrossing and almost mesmerizing.
The workout is challenging, but the techniques are simple, well constructed and practically elegant in how it all ties together to get you kick ass fit through "muscle confusion."
The 12 DVD are $120, and may seem pricy at first. Its a bargain if you consider its 90 workouts over 90 days thats like $1.33 a workout...compared to a personal trainer at $60 per session P90x pays for itself in two sessions. You do need to buy some stuff like a pull up bar ($25) and resistance bands ($11) and a yoga mat.
You know a product works when literally thousands of people post up YouTube videos of their amazing Before/After transformations. I did make made a Before Video, but right now I am too gun shy to share it with the world...I may feel different in 90 days. If you really want to see it, email me here.
In the mean time check out these awesome P90X transformations:http://www.youtube.com/watch?v=6YQJEQOnpvM