Hi, I did P90X for several years and one of my friends just bought the Insanity. It looks interesting. Personally I have changed my focus to simpler muscle building (not bodybuilding) routines.
I think the P90X/Insanity style workouts are so long and grueling that they are not conducive to gaining muscle. I think people can get great physiques with three weight training sessions a week, clean diet, and very little cardio. Using intense routines that go five or six days a week for 45 min or so is not sustainable and eats into the bodies recovery process.

Just my two cents, hope you don't mind me saying