Artifacts have long been some of the most powerful cards in Magic the Gathering. In fact six cards out of the Power 9 are artifacts. This artifact may not have the same power as a lotus or mox but is still very useful. Not on that but the cost of thi artifact is very reasonable. It only costs two mana.
What Mind Stone does is to provide mana. It helps accelerate decks. This is especially useful in control decks or artifact deck which require a lot of mana to work.The card provides one colorless / generic mana for you to use. As an added bonus, the card could be tapped for mana the moment it comes into play. Another notable thing is that the artifact could also be sacrificed for a card draw. This is important in the end game when you have too much mana lying around and nothing to do with it.
It is hard to imagine that this card was a mere common in its original incarnation in Weatherlight. I highly recommend this card for Magic the Gathering players. It is extremely versatile and low in terms of mana cost. This card is good for both casual and tournament play.