In case you hadn’t yet seen it, I did a review on Top 8 Magic about Glacial Fortress, the U/W M10 dual land that was recently spoiled on the mother ship.
To wit:
Glacial Fortress
Glacial Fortress enters the battlefield tapped unless you control a Plains or an Island.
T: Add W or U to your mana pool.
We can safely assume (even without using spoiler sites, which I don’t typically reference, ever) that Glacial Fortress is the first in a new line of M10 dual lands… though whether we have five dual lands or the full ten dual lands (including enemy colors on the order of Sacred Foundry, Breeding Pool, or Godless Shrine) is a mystery at present.
What interests me is the potential Constructed — specifically Standard — impact of this cycle. I actually wish I could write about a B/R or G/R version, but I don’t know the names (at least not officially) at this point 
Regular readers of this blog know that I have been fooling around with ye olde Cascade decks recently, pushing Bloodbraid Elf and Bituminous Blast into more (and less) interesting molds, going for more consistency or — surprisingly — less speed as the case may be with the Rhox Meditant deck. One of the things that I have found to be less satisfying with the decks is their mana consistency. The attack-oriented build, for example, often has strange — if recoverable — draws due to the conflicting tension of being a three- and four-mana haste aggro deck… that has a Reflecting Pool Control-reminiscent mana base with a ton of comes into play tapped Vivid lands.
One idea for a new build would be to try to take advantage of Ball Lightning (which has also been confirmed) as Bloodbraid Elf’s new best friend. I won’t speculate a full listing at this point (because I don’t really want to talk about Lightning Bolt), but there is ample design space to go with a much more concentrated Mountains mana base, touching the Black and/or Green equivalents of Glacial Fortress, reaping considerable speed, if spending a bit of flexibility.
You would of course have to give up Steward of Valeron, but might end up with a much more consistent package. For example shifting to a B/R build you could bias for Sygg, River Cutthroat* as the two drop over Steward of Valeron, run Blightning, Boggart Ram-Gang, and Ball Lightning in a jazzed three spot, still pack Bituminous Blast, with just the mildest Bloodbraid Elf splash out of Green. That is, if you were willing to invest the same twenty-six slots on lands that we did in the Primal Command deck, you would easily have space for ten or even twelve basic Mountains, along with the B/R or G/R equivalents of Glacial Fortress, with Savage Lands as the lonesome land that is guaranteed to come into play tapped. If you don’t get lucky on Mountains pulls in your opening hand, you are really not that much worse off than with a double-digit Vivid count… Because you have structured your spell selection differently, it’s not like you are shut out of a color you actually have to have under pressure (probably).
This is all intensely speculative, of course.
With the mana really and truly awesome there is just no incentive to playing mana-consistently whatsoever. You just end up with a worse, weaker, deck if the baseline is multicolored Bloodbraid Elf any- and everywhere, presuming passable mana (as opposed to stumbling mana, as in Block, where G/W was able to prevail on greater consistency and brutal speed).
Which actually brings us to a different point… If that is the case (and it just might be), the Glacial Fortress cycle of dual lands might be next to unplayable in Standard!
That’s right! If we continue to play decks with 1-5 basic lands (and even then only because we think someone might be playing Path to Exile) — especially when we don’t even play a second copy of any given basic land — Glacial Fortress and its buddies really aren’t much better than Coastal Tower… In fact, in-format, they are just worse than Arcane Sanctum. Surprising, no? Again, very speculative
Two interesting points arise from this line of thinking:
1) There is actually an interesting [deck] design space here. Do you ignore Glacial Fortress and continue to play with crazy Arcane Sanctum / Vivid land-based mana instead of going for “more consistency” which might mean less power?
2) It’s rare that cards are kind of crappy in Standard but are quite good in Extended. Glacial Fortress seems like an awesome brother to Hallowed Fountain (or any of several Plains- or Island-based dual lands from Ravnica Block).
… Just my next few semi-spontaneous thoughts on Glacial Fortress
LOVE
MIKE
Currently Reading: Fables Covers: The Art of James Jean Vol. 1
* No, I didn’t miss the potential of Lightning Bolt (still don’t believe it) and Sygg as a kind of punishing Impulse.