You do it from hand, so its not as telegraphed as, say, Blast Zone, and its much harder to interact with an activated ability than a Nature's Claim
This is a 5 mana card that essentially draws you two cards, so one card less than something like Jace's Ingenuity or Precognitive Perception, both of which were already playable
The games depth, storylines, and varied expansions have created a huge secondary market
Haven of the Spirit Dragon works for any color dragon deck, and Cinder Glade benefits from having basic land types to work in conjunction with Game Trail
Later in the game, the impact of this card is reduced a bit, since just one mana probably won't make that big of a difference on turn fifteen or more, but the explosive early game it can provide is impossible to ignore