The only matchup that I truly fear with the "Black Mask" deck is some WW variants that are loaded with hate.
I have been playing this deck for about a year now, and have done extensive playtesting against most of the major archetypes. No, I'm not going to give a win percentage or other silly stats like that, but I'm quite confident in my knowledge of the archetype.
First, a few comments on Gzeiger's deck. You need additional threats aside from the combo. If your only threat is the Mask itself, you are going to get run over most of the time, there is too much that can go wrong. The combo is strong but almost all archetypes have answers for it. You also need to just stick to swamps and snow covered swamps. The weak mana base is a liability. If you splash something it better be worth it (I currently don't think it's worth it to splash another color, and believe me, I have tried all of them).
Cursedscr - CF's version of Mask, which is similar to what I play, is a very well rounded deck. There are options, you don't just fizzle out and lose if you don't get the mask+nought out.
CF - as always, you are the voice of reason on this subject.
Tatanka - You played CF's version and you lost 12/13 games against Stacker? I would not say that Stacker is an easy matchup, but it is certainly better than 12/13. Pointers for the matchup, speed is of the essence, I would probably mulligan a hand that does not produce the combo in turns 1-3. You also have to understand that, if you play a full complement of moxes, you are more vulnerable to the Welder's ability. And if they pack Viashino Heretics maindeck you are screwed if you are not in business before it is cast. Your sideboard should address killing the offending critters.
Max - If you are referring to the deck posted above, you are right. But that's hardly the case against a deck that has a more well rounded threat base. Another thing, if you play mono-blue and you play Null Rods, you lose the ability to use Moxes and Powder Kegs. The loss of moxes slows your deck down significantly. And the loss of Powder Kegs means that you will lose if I get the Dreadnought in play. Without moxes, you'll be dead before your Control Magic is any good. If you don't play in an environment with moxes, then disregard this.
Powder Keg is annoying. But remember this, if you play a Dreadnought with the Mask, when it comes into play, it's face down. This means it's casting cost is 0. Your opponent has to wait for you to turn it over to blow the Keg at 1 to destroy it (if they blow it at 0 you just turn it over in response). So at this point you can cast another Dreadnought, turn one over and attack, the opponent either takes 12 or blows it up, but this does not affect the face down one. Then next turn the other one does it's thing. Multiple Kegs = PROBLEM.
Like I said earlier, I'll take my chances against any deck with a Mask deck. Of course I'm going to have a hard time winning against some stupid WW deck playing 4 Seal of Cleansing, 4 Swords to Plowshares, and 4 Null Rods. Notice I said "Seal of Cleansing", you can't Disenchant a face down Dreadnought from your hand, so the odds are that I will Duress/Hymn you before I attack or you use that Plow, I gain 12, giving my Hippie the time he needs Besides, we all know that WW is a major tournament contender in type 1, also making numerous appearances in the top 8 ;-)