Well the bloodburster is definitely just the beginning of the crazy shit in the Covenant expansion. I was able to finally go through all of the cards and here are some other noteworthy things:
--a hazard that puts the whole Barracks into cryosleep by wiping them and putting new ones in facedown
--a hazard that puts each player into stasis meaning they can't discuss strategy, coordinate or heal with one another
--an event that kills the top card of the barracks and then all copies everywhere
(hands, decks, discard, etc.)
--several enemies that say if you draw a Close Call or Flesh Wound strike you have to draw again
--two final enemies
that represent both aliens in the film; have to be killed on the lander and the terraforming bay
--after killing the final enemies you can decide if you want to finish or go ahead and try to kill David by using an added objective 3b card;
he has four different avatar cards that you randomly pick from and they all have seriously bad abilities
--similarly to the Queen Mother mode, you can play as David against the players and have your own hand and deck
On the good side there is the new Covenant
keyword letting you grab another adjacent barracks card when buying one and there are several new avatar characters that seem to have decent abilities.
Haven't been able to play again since GenCon but it seems like a lot of new interesting ideas that will give varied and creative gameplay. And it definitely looks like it retains if not surpasses its previous difficulty. Overall I would definitely give it a thumbs up if you have liked the previous material for the game.