The Havoc is a good head with a good design. It will certainly kill if you put it in the kill zone. The blade retention system is not bad at all but you still need to inspect them from time to time to make sure they are engaged just to be safe. Only issue I saw with them was the ferrel would break away from the post if it hits something hard. I think they may have change the metal in new versions to prevent that. I know on the dead meat the post and ferrel are separate. Long story short, they will serve you well if you do your part.
