There are LOTS of threads on here about P90X. It is a really awesome program & I love it! I'm doing my 3rd round of it now, it's given me strength, definition, and flexibility too! A lot of people that are used to Cathe's cardio & lower body find the cardio not as difficult. I would agree w/ that. I'm a runner, so often times I sub in a run for a cardio workout.
I even became a coach because I love the program so much so if you have any questions feel free to email me. (click on the link below for a link to my email)