I could talk about it here. I took a look at it and here is my take:
It all depends on how you want to look. If it is you in your avatar, then you will be more defined. Maybe even a 6-pack. It will make you "cut", but not "buff". And you look like a thin guy. Its good for people trying to lose weight.
My problem with the P90x is that you are only really limited to your own body weight for resistance. Basically, bigger weight means bigger muscles. And, there are other things you will have to buy other than just the DVDs. Like a chin up bar and elastic straps. They dont really tell you that.
Then there are the suppliments. Yes, these are important, but they will sway you to buy their own brand. Again, not something they tell until AFTER you buy it. And unforunatley, they are right. You do need that stuff.
Look, a system is system. The P90x is well thought out. You will not go wrong with it if you are trying to get into shape. I just dont like the end product for me. I like having that "buff" look with big muscles. I weight train. And nurtrition is a hobby of mine.
So if you dont want to think, research, read, study, be prepare to spend money on people who will think for you. For me, its a labor of love. But Im not you. Any more questions, let me know.