Ive used it before and it does exactly what its supposed to do. It built my ABS and got me back to where i was in high school which is exactly where i wanted to be. And if it works for me then it can work for you too. Great way to build the ABS you want.
Love P90X's Ab Ripper X: Do 25 of each 1.In & Outs 2.Bicycle (2 sets, one forward, one backward) 3.Seated Crunchy Frog 4.Cross Leg/Wide Leg Sit-up (Not shown) 5.Fifer Scissor 6.Hip Rock’N Raise 7.Pulse Up 8.Rollup/V-Up Combo 9.Oblique V-up 10.Leg Climb 11.Mason Twist (50 reps, not shown)