It's an excellent answer to an opposing combo, and circumvents most counterspells since your opponents can't cast anything in response
Knowing youre the only one that can play combat tricks or removal spells during combat makes it much easier to decide who to attack with what creatures
Four mana is accessible early without issue in green, and the payoff is well worth the price of admission
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
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