Some of them are pretty intense if you're out of shape. I stopped doing them and just got a gym membership b/c I wouldn't ever workout at home. After a couple months of going to the gym 5 days a week I remember doing the chest and back workout for p90x when I was at home one day and it was cake.
The plyometrics workout is pretty nuts though. That one is an ass beater. If you can find that one, it's the one to have.