The Mass Chaos is a great compliment to both the Extreme Chaos, if you are looking for a bit more hook. And also to the Complete Chaos, if you are looking for a bit less hook. As you can tell, the Mass Chaos fits in between the Extreme and Complete.
The Mass Chaos gets through the heads cleaner than any of the prior Chaos' and stores up a lot of energy on the back end. In my experience with the test ball I received, I took the shine off of the ball to make it easier to compare to my other Chaos'. The Mass Chaos rolls similar to the Extreme, but has more continuous arc through the back part of the lane. Thus, a bit more overall hook than the Extreme Chaos.
After throwing the Mass Chaos, I think it is the most versatile of them all. A great addition to anyone's equipment line.
Lastly, for those of you who are wondering, I drilled mine with the pin 3 3/8 from my PAP and with the mass bias marking in the strong position.