You need at least 3 chainsaws on every ladder chokepoint — and one just down the path for those that slip past — “look out!”
Sorry that clip is really really short. Check out theChainsaw Massacre mutation now on L4D2. Hordes, Tanks, Witches, all will drop before you. Greet all infected up close and personal like, even the boomer (their bile can only more points your way). The only thing to fear, is fear itself. In my dictionary, fear itself is defined as “three blokes in the vicinity running about with very large chainsaws and very little restraint.” Good times 
Looks like fun. I hope eventually many of these mutations become permanent. I’ll miss some of them.