I have done 2 full rounds of P90X, and I use it on and off for my usual workouts. I highly recommend it. It helped me lose my 110 lbs since June 2010. I also like Insanity,and I'm getting P90X2 for Christmas. Also recommend Rushfit and The Pit.
Update on my weight situation: I was diagnosed in September with hypothyroidism and low testosterone. All summer long my energy was shot, I couldn't really workout, and I had violent mood swings. I'm now getting (shitty) treatment and I'm due to see an endocrinologist in a few weeks. My metabolism is basically dead, I'm too tired to exercise, and I'm always low-energy. I also can't "keep" muscle, no matter how much I lift and eat protein. It really sucks.
I quit weighing myself in September. I had lost 10 lbs eating according to the primal/paleo diet, which I still follow as close as possible. But due to my medical issues, I've decided to stop stressing about actively losing more weight. Once I get that shit figured out, I'd like to lose another 20 lbs. At this stage, I just want to be able to workout again. I miss the "high" and the pump. The fat loss comes with it, but I just miss how it made me feel. Sitting around feeling fat and tired isn't fun.