A resounding YES!
I will qualify this by saying I know I will need to schedule my matches around the “easier” P90X days. Today was Yoga, so I did it first thing this morning. I ate more throughout the day and increased carb intake. My tennis match was at 4 pm, I took two advil prior to and did some light stretching. Here’s the result: I won 6-3, 6-3 against a guy who whooped my butt last fall. I don’t want to overstate this, but it’s like it wasn’t my body. I was getting to the balls, hitting in position (Plyometrics). I was hitting the balls deeper, following through and chipping shots back over the net that would have died on my racket in the past (Ab Ribber X, Kenpo X). My legs felt great, my core felt great and I was hardly breathing. All the aeorbics helped big time. I took my opponents legs and his spirit out from under him. I beat him with fitness. Did I say I’m in a good mood?
Anyway, today was the most tangible day for me to see what I have gained from P90X. Keep pushing “play.”