Yeah, Hand of Gul'dan is stupid good. I've been playing some zoo and some games the deck looks so completely broken, but when you don't pick up a hand its very unimpressive. I feel like I've been extremely unlucky while playing the deck. I've started mulliganing strictly for hand because there is a good chance you'll get a librarian or nightshade matron and with that it gives you the tempo to win most games, but I had a huge string of games yesterday where I couldn't get a hand to save my life. The cool design with hand is that it doesn't really work in a control warlock deck since you'll have cards with costs greater than 6 and you typically don't want to throw those away.