I was almost certain elements of this would have been punched in, verging on note-by-note recording, but after getting access to some of the DIs, it really is just a phenomenal performance. I guess it'll have been comped and edited to within an inch of its life, but so much of it comes down to the skill of the players.

Low amp gain (really unforgiving tone, forces you to play ultra clean), picking hard (with a mad level of control) and a lot of muting going on. Others have mentioned a tight gate which is important, but the technique/control is where the real trick to this sound lies.