Personally, I strongly dislike the combo in U/G lists, strongly dislike the combo in Mono-G BoozeCube-style lists, and use the combo in Mono-G John Kassari-style lists. This combo works in Kassari's lists in part because he utilizes
Into the North to fetch both basic snow lands as well as
Dark Depths itself. This is a luxury you won't have in U/G lists or a BoozeCube list. For the other lists, for every win you snag out of nowhere, there are at least as many, if not more, games where the combo is clunky and awkward, ends up in my hand, or otherwise puts me in a situation where I wish the cards were pretty much anything else. Also, you'd probably almost never want to fetch out the pieces with
Primeval Titan:
Thespian's Stage will enter the battlefield tapped. This wouldn't matter if not for the fact that if you're tutoring for "I want to win now", you'd probably rather just get
Cloudpost and
Eye of Ugin, then
Cloudpost and
Karakas, and take all of the turns with Emrakul. This leaves your opponent with no avenue to do anything.
If
Dark Depths ends up in your hand, you're usually in bad shape. If either piece ends up getting hit with
Wasteland or is discarded, you're in bad shape. You need at least four lands - Depths, Stage, and two lands that produce mana, barring playing against another Cloudpost deck - to even attempt to activate your combo. If Marit Lage ends up eating a
Swords to Plowshares or a sacrifice effect, you're down to two lands. In contrast, you can cast
Primeval Titan on four lands, putting you in a far superior position. The reason this combo works well in Lands shells is because you can vomit out multiple lands per turn (
Exploration and
Manabond), reduce the land requirements for activating the combo as well as give the lands themselves something to do before you combo off (
Urborg, Tomb of Yawgmoth), and easily get binned pieces back as often as necessary (
Life from the Loam). Loam plays very poorly with Eldrazi, and if you start adding in other cards to enable the combo, now you're just playing CrappyLandsShell.dec.