This is one case of a song making a huge change as it developed. Originally it's distinguishing characteristic was that it was just super fast at the risk of being messy. I think it's really evolved into something that is complicated in a very elegant way.
The Fallout also features something of a solo in the rhythm section and the lead guitar is playing the same thing. It moves in a way I like a lot and I may try to do this more in the future!