As far as what silencers are made of... I do not know, that is something that they've kept to themselves since they first came out and were refereed to as NRConduit.
The Highlife is very different, New shape to the nose and tail, the nose is softer, there is more pop in the tail with the popwalls now, The Hybrid All-Mtn Rocker is the same, the UL Stringers were dialed down a notch to make it a bit more lively and it carves more like the Berzerker does. Since there is some interest in that board I'll make it one of the next videos I upload to my channel.
The Berzerker is unchanged for 2013, just a new graphic.