Every single "I've got the codex, ask me questions" thread I've seen has failed to ask the single most important question that knocks on onto *every* other aspect of the army.
How do the three new instinctive behaviours work, and how does synapse work now?
Every other change is secondary to that, in my opinion...
If a unit isn't in synapse, LD test then either "hunt", "feed" or "lurk" roll. Can't remember them exactly but lurk is defo fall back if you roll a 1-3.