I have been keeping up on my P90X too!! Yesterday was plyometrics, I haven't done those since highschool. I couldn't even finish the last 10 minutes, my legs felt like they would collapse if I tried to jump anymore. It's the toughest cardio workout for the program though, so I didn't feel too badly for stopping early.
Today was biceps, triceps and shoulders, plus the Ab Ripper X, yow!! My abs are still pretty tender from Monday but I toughed through it. Only 86 days to go ;)
I think I may have to wait about a month to start running, I need to get my body used to doing all of this lifting activity before I add anything more!