Just noticed that this thread got active again, so thought I'd update:
I did not do all 90 days of P90X. I made it to about 80 days and then I just needed a break.
The good news?
I lost 19.8 lbs, am 4 inches skinnier around my waist, and am way stronger and fitter than I was before. This has really helped my body recover from my second pregnancy, too. Losing weight and gaining muscle really helped all the pelvic and lower back alignment and pain issues I was having. (I did a lot of physiotherapy for that, as well.)
I have decided to go ahead and join my husband on the Insanity workouts next. I'd like to try to shed another 15 lbs before TTC again.
Overall, it was successful for me, but I have to say that this is a really hard regime to get through with little kids. You have to make it a priority.