Has anybody else done, or is anybody else doing, the P90X system by Tony Horton? Holy moley! I'm on Day 4 of the "Lean" program, and man, I have been so sore the past few days! It's kind of awesome that I actually feel better while working out (as the sore muscles are getting a bit more use, and don't have time to hurt). I keep hearing that people tend to drop off the program around Day 30, and I'm truly hoping I can push through to all 90 days!