I got great results with P90X as well. Specifically a big increase in muscle tone and I looked more "ripped." I didn't get as many strength gains as I did with STS, but I was still happy with the physical results.
The program is very, very repetitive. It's not like STS, which I have done over and over again. I was able to stick with the P90X weight work, but on cardio days I would do 60 mins of my cardio of choice instead of the PlyoX and KenpoX. But, I pretty much stuck to doing 2-3 cardio workouts each week...60 mins each session... (to get to 3 cardio workouts, I would do cardio instead of Yoga X).
Ab Ripper X, however, is one of the most intense ab workouts I have done, so IMHO it is worth doing as the program recommends despite the fact that I got totally sick of it.
The biggest issue was, as always, diet. I didn't follow the food plan, BUT I cleaned up my eats, focusing more on proteins, fruits and veggies ...eliminating most processed carbs, except for a 200 cal treat each day.
ETA: I also subbed in a Cathe leg video for leg day most of the time. Cathe is hardcore with the leg workouts; Tony is not.