Okay, first up: one card I really don't understand. I understand what the card does and everything, I just don't understand why everyone thinks it's so amazing. Tapping to add a colourless - good. Not coming into play untapped - good. Paying 1 and tapping to tap a land - not so great. Think about it: you're tapping 2 of your lands to tap 1 of their lands. The trade just isn't worth it.
In set, this card was awesome as Masques was really slow mana-wise. However, outside of set this card is not that good. There are 2 scenarios in which I can see this being used. The first is to tap a dual or multi-land when your opponent is mana-screwed. Yes, this is a good idea, however you are screwing yourself over as well because you're losing 2 lands (or a land and a mana rock) in order to tap down their land. The second scenario is to tap down a land in order to slow your opponent down. If that's the case, your master plan is defeated when they make their land-drop for the turn.
Sure, there are certain situations where this is useful (Cabal Coffers, Gaea's Cradle, Tolarian Academy...) but they are too few and far between to warrant the $40 pricetag this card has currently.
Pros: It comes in untapped and it produces colourless (for colourless EDHs?)
Cons: The secondary ability is pretty useless
Alternatives: Icy Manipulator, Wasteland (for nonbasic lands), Strip Mine, any land destruction, Early Frost