Since that first half marathon I have completed another at the Manchester City Marathon this past November in a PR of 1:49:46. I was also part of a 200 mile relay team that ran from Northern NH to the Coast of NH in just over 28 hrs. I completed a total of 17.5 miles over 3 legs at a pace of 8:04.
I am currently training for my first full marathon in Vermont on May 30th with the help of P90X. In my experience P90X with running is a great combination. Many times (I know this from experience) runners neglect to incorporate weight training with their running or only train their lower body. Weight training combined with the flexibility training of yoga and running is the ideal training recipe. Just remember to listen to your body for any signs of overtraining and take those rest days when needed.
If you have any questions about combining P90X with running just send me a message.