If you do a search in this forum, you'll find some useful threads from several months ago.
I did a 90-day rotation (actually took me about 110, because I filled in with some other workouts and took extra rest days)a while ago. I had excellent results in increased upper body strength and definition, core strength (after doing P90X for a few weeks, I tried pikes on the ball and could do them for the first time!). I did need more lower body work (but I'm 48, and an ecto/endo--not favorable for muscle growth) but supplemented with some heavy leg presses/squats on my Rockit.
I didn't follow their nutrition plan or take their supplements, but I did take a soy protein drink (Power Dream, chocolate flavor) after my weight workouts, and it has a similar breakdown of macronutrients (protein/carbohydrates/fat) as their recovery drink.
The before and after photos are often of people who have used "BeachBody products," so they could have used Power 90 or something else before P90X.
P90X has become my benchmark for excellent weight workouts. I'm testing Cathe's Hardcore against it by doing a "P90X-like Hardcore rotation"(I've posted it in the "rotations" forum). Thought it was only fair to give her the same chance I gave to P90X.
P90X is rather low on cardio (and with a purpose: it focuses on muscular strength and growth, and does enough cardio, but not so much that it starts being detrimental to those goals). Some people who did P90X the same time I did added extra cardio, or (as I did) sometimes substituted other cardio workouts (I used KPC in place of the P90X kickboxing workout every once in a while).
I think it's an excellent investment.