I like a lot of the big minions in this set. 6/8 taunt for 7 mana (Ironbark get rekt), 8 mana 6/10, 7 mana 5/5 Windfury Beast has potential with Tundra Rhino. They all have awesome art, and steer the random Minion curve up.
However, there's some really interesting stuff going on with the cheaper minions. 2/4 Taunt for 3 mana (mini Sen'jin), 1/4 taunt for 2 mana that even gives C'Thun taunt. Then there are the aggressive cards: 2 mana 3/1 Stealth in a world where you can already run Infiltrator, a bunch of class 1 drops, 3 mana 2/1 deal 2 damage (and buff C'Thun, nuts with Brann), 3 mana 1/5 Warlock card that gets buffed after each friendly summon (scary in Wild with Haunted Creeper on Turn 2). Some of these cards with fancy effects have keywords you might miss the first time. For example, that 2 mana 3/2 Mage minion with C'Thun synergy actually has +1 Spellpower.
I think one card in particular to watch out for is Forbidden Ancient (Druid card that with X/X stats where X is the mana spent). This is pretty crazy with Brann, getting more and more undercoated the more mana you spend on it. Kinda gimmicky, but it might see play somewhere.
I don't know how many of you watched the stream, but one highlight was the Shaman player going Hallazeal->Elemental Destruction->Eternal Sentinel(Shaman 2 mana 3/2 that unlocks mana crystals) for a board clear and a full heal.
Edit: I also like how they brought back the enrage mechanic a little bit. That 4 mana Taunt for Warrior is one of my favourite cards in the expansion. If you don't kill it, Warrior will activate it's enrage and kill one of you mid-sized bodies.