PV went so far as to say that Stoneforge Mystic is the Bitterblossom of their UW builds and that's the reason why they run four maindeck Mystics but only 2 maindeck equipment. The deck looks really cool and has decent matchups against the field the worst being either Valakut or Vampires in game one.
Here is PV's Deck List (Ben Stark also played it to a 1st Place Finish in PT Paris):
Lands:
4 Celestial Colonnade
4 Glacial Fortress5 Island
1 Misty Rainforest
4 Plains
4 Seachrome Coast
4 Tectonic Edge
Spells:
4 Squadron Hawk
4 Stoneforge Mystic
4 Day of Judgment
1 Deprive
3 Gideon Jura
4 Jace, the Mind Sculptor
3 Mana Leak
4 Preordain
4 Spell Pierce
1 Stoic Rebuttal
1 Sword of Feast and Famine
1 Sylvok Lifestaff
Sideboard:
2 Baneslayer Angel
1 Deprive
2 Divine Offering
2 Flashfreeze
4 Oust
3 Ratchet Bomb
1 Sword of Body and Mind
The deck basically sides out all the counters for the aggro decks and sides in the removal and Baneslayers. The Valakut sideboard is out with the Hawks, a Gideon, and the Lifestaff and in with the Flashfreeze, 2 Oust, Sword of Body and Mind, and Deprive. For control it depends on what you are facing. For example, against UB I would cut the Staff for another Sword and maybe squeeze a Deprive in there if I thought it was necessary. Against the mirror I would bring in Sword of Body and Mind, and maybe a Baneslayer for the Lifestaff,1 Spell Pierce. Against the Quest Decks and Tezzeret Decks I would bring in the Divine Offerings in place of counters depending on how game 1 went along with ratchet bomb for quest.
Because I really liked what the deck looked like on paper I built it and tried it out versus Valakut. Most of the games were pretty ridiculous with someone blowing the other person out. In games where I didn't Oust a turn 2 Cobra it was very difficult to win. The new Valakut decks drop Titans like a boss (turn 3 is not uncommon) and Green Sun Zenith gives the deck a lot of versatility. It is really crucial to have turn 2 Mystic in this match up because otherwise Valakut can get a head of you on lands pretty quickly. But Feast and Famine changes that a lot. Body and Mind is good too because you can mill Titans (or even their deck, I won a couple times that way). While I really like the way this deck configured I think it could use a little adjustment to help against Boros and Valakut.
This is the list I will be running:
Lands:
4 Celestial Colonnade
4 Glacial Fortress
5 Island
1 Misty Rainforest
4 Plains
4 Seachrome Coast
4 Tectonic Edge
Spells:
4 Squadron Hawk
4 Stoneforge Mystic
4 Day of Judgment
1 Deprive
3 Gideon Jura
4 Jace, the Mind Sculptor
3 Mana Leak
4 Preordain
4 Spell Pierce
1 Stoic Rebuttal
1 Sword of Feast and Famine
1 Sword of Body and Mind
Sideboard:
1 Baneslayer Angel
1 Elspeth Tirel
1 Mindbreak Trap
1 Sylvok Lifestaff
2 Divine Offering
2 Flashfreeze
3 Oust
2 Ratchet Bomb
2 Condemn
The changes I made should help improve both the Boros and Valakut match ups. The Sword of Body and Mind is better against Valakut, Control Decks, and Elves. The Lifestaff is better vs Vampires and Boros. I think it is better to have Body and Mind in the main than the side to help against those decks, the Lifestaff can come in from the board against Boros and Vamps. Oust and Ratchet Bomb are each reduced by one to make room for 2 Condemn which are better than either of those cards in the Boros matchup. 1 Baneslayer became a Elspeth Tirel because Elspeth is better vs Vamps than Baneslayer and without Sylvok Lifestaff main you want make sure your board is still good for them. Mindbreak Trap might seem like the most odd choice. My thought process was to cut the Deprive for a Flashfreeze against Valakut because I really didn't want to lose any games against Valakut because I had Mana Leak and my opponent could pay for it. But then I also remember that Valakut was gaining control by being much more aggressive in the early game and if you didn't have Mystic on turn 2 with and have Spell Pierce on turn 3 and be able to drop a Sword into play you were really behind. The other thing I noticed was that Valakut is playing a significantly higher number of spells per turn since the addition of Lotus Cobra. It was only during those games where Valakut had a ridiculous good turn in the early game that I lost. Mindbreak Trap is perfect for this matchup now. Before it was U/B's tool for countering Gaea's Revenge. Now you can actually cast it against Valakut for 0 mana and "counter" anything
without triggering Summoning Trap. Even if they didn't have Summoning Trap maindeck they most definitely sided it in. Mindbreak Trap becomes a lot worse against other decks but is not as bad as it was because with SOFAF you play something and untap your lands leaving mana up for Mindbreak Trap that you couldn't before.