I tried the dreadsteed deck first, won that game, but then swapped to freeze mage as an anti-warlock deck and I'm 4-0 against them. Unfortunately, you lose to some of the other decks, like patron warrior or any deck that doesn't have to over commit to the board, basically. You only lose to patron because the warrior can just armor up a ton and you can't burn through it all.
I ran frost bolt, ice lance, ice block, doomsayer, frost nova, thalnos, fireball, forgotten torch, arcane intellect and medivh's valet. I didn't run Alexstrasza because you don't really want to draw a 2nd one ever, but if everyone starts playing warrior you might want to.
It really does wreck warlock though. They basically have to fill their entire board and then you just nova + doomsayer to clear.