I've never tried P90X. I just go to the gym 4 or more days a week, do some calisthenics at home, and hit my heavy bag. I've seen results after six months of working out "religiously".
I've tried creatine, but cut it out because I want to take as few supplements as possible. I still take whey protein to get more protein without having to eat tons of food, but I'm trying to avoid other supplements.