Interesting to note that all tyranid psykers are mastery level 1 except the swarmlord. Each psyker may exchange powers they come or purchase with discipline powers.
A tervigon (with dominion) can but catalyst and onslaught and exchange dominion and onslaught for biomancy, telepathy, or telekenesis. Mastery level 1, but up to 3 powers.
Zoanthropes can give up lance and blast for 2 others.
Broodlords can give up aura and gaze for 2.
Tyrants must take 2 from the normal list and then can swap them for 2 others.
DoM can give up cataclysm for 1 discipline power.
Swarmlord gets all 4 tyranid powers and can swap up to 4. Looks like I'm getting the new kit lol. Paroxysm + 3 biomancy powers anyone?
Not much else has changed. Deathleaper has 2+ cover now, but most cover has moved to 5+. Broodlords can chellenge sarges and then hypnotize them. Tyrants with guard are now treated "exactly as if they had the IC rule", but the guards can take the "look out sir" rolls. It still appears outflanking genestealers cannot assault when they arrive.
Playtesting the bugs today. More feedback to come post games.