It's an excellent answer to an opposing combo, and circumvents most counterspells since your opponents can't cast anything in response
Sea Gate, Reborn is mana when you need it early, and Sea Gate Restoration is draw when you need it late
Fortunately for you and unfortunately for your opponents, because Blightsteel Colossus is indestructible, if they dont have an exile card, a creature 11 power or greater, or a horde of creature tokens with a total power of exactly 11, the game is done
Beyond the names and creatures youd expect, this extends to creatures such as Bill the Pony
In Commander its an auto-include in colorless or artifact deck, too
On the flipside, if your key engine costs a ton of mana, like Kozilek, the Great Distortion, a big beefy ramp card like Thran Dynamo will get Kozilek out much earlier than a Mind Stone