(Sneed's Old Shredder is neutral.)
For the classes, the one I've played with is Vol'jin, and it's looking like an auto-include in every Priest deck. It's really strong. I haven't looked at strong Priest players to see whether they use it, though.
I haven't played with any others yet, but I've had Troggzor played against me in ranked play, and that was quite awkward. It's a bit Cairne-like in that if you use a spell to remove it, it leaves behind a body, but unlike Cairne, it's harder to ignore because it spams bodies onto the field when you use spells for other things, too. Of course, it's 7 mana vs Cairne's 6. Still, I wouldn't be surprised to see it replace Cairne in many decks, given that 4 attack on a high-value minion is almost a liability against Priest now due to the Shrinkmeister+Cabal combo.