Hearthpwn

So, quite a bit of brewing went into this deck, with which I just got to legend 130 (climbed on phone so no exact stats). 

Matchup summary 

• Aggro decks (Odd rogue and secret mage, plus some variants of even shaman) are not great matchups (mage is better than rogue). You do have Reno (plus another full heal in Shudder), and many ways to slow down the game, but sometimes you get completely run over.
• Combo decks are generally fine due to Dirty Rat and transform effects. Quite a few Mecha'thun have become murlocs during my climb :)
• "Big board" decks (Renolock, Big priest) depend quite a bit on transform effects, but there's also some nifty things you can do combining Mind Control Tech and Dirty Rat
• "Build a monster" decks (Handbuff paladin, Mech Hunter)  are generally good matchups due to all the transform effects.
• Super long-game oriented value decks (Reno mage, Control warrior) are very easy due to the OTK finish

OTK finish:

Against slow decks, Shudderwock acts as an effective OTK: Make sure you either have played 2 Loatheb through bounce effects, or keep the coin to do hero power - Shudderwock. Doing this after a few Jades creates a basically impossible board. If you have played Eater of Secrets, it also deals with Ice block - this makes your matchup against slow (Reno) mages and warriors a breeze.

Mulligan guide:

• Keep quest against everything other than Rogue
• Keep up to 2 early drops. Order of priority is: Questing Explorer (with quest), Zephrys the Great,Jeweled Scarab, Lackey generators, Novice Engineer, and, lastly, Jade Claws
• Keep a 3/4 drop if you already have an early drop
• Keep Jade Lightning against Rogue
• Keep Plague of Murlocs and Hex against Priest and Warlock
• Keep Devolve against Paladin, Shaman and Hunter
• Keep Eater of Secrets against Mage (duh!)
• Keep Reno Jackson against everything except Priest and Warlock.