I loved insanity for the first two workouts. I could tell it was kicking my ass into great shape, but, after that I noticed my ankles where taking a serious beating along with my bad knees from baseball, I was a catcher all the way thru college so my knees have some serious issues.
It's a great high intensity training tho. I can see it helping with explosion strength I'd recommend to any wrestler, baseball or football player looking to condition for the upcoming season.