congrats on getting P90X....if you can push yourself and stick with it, you'll be happy with your results. Do note, that most people don't see the bulk of the changes until the third month/phase. I hit my target weight pretty quickly just by changing my diet...but if you're wanting to get cut, it'll take a couple months before you start seeing the majority of the results.
I did the program starting last April until around mid Fall this year. Once football season and the holidays hit, I was off my routine and eating crap again. I'm getting married in 5 months and my goal is to start the program up again here soon so that I'm ready for our honeymoon on the beach!
The best results I experienced were cardiovascular wise...surprisingly. I found the plyometrics workout helped me immensely for my indoor soccer team I play on with a bunch of guys. Pretty soon I was agile like a cat and able to stay in the game for the whole 50 minutes!
btw, if you want motivation, check out this guys thread. Incredible results:
http://www.weightloss-hq.biz/weight-loss-forum/p90x-before-and-after-pics/paulyp-s-final-pictures.html