Yeah, the untap lands mechanic from the Urza's Saga block was a mistake, but I still like it. If I didn't use the untap lands mechanic, the casting cost would be 2U (closer to
Psychic Theft, but a little more expensive because there would usually be more instant and sorcery cards in an opponent's graveyard than in an opponent's hand).
What do you mean by "give you the card permanently"?
If you're paying 3UU to counter a spell, you're not going to have much extra mana to play an instant or sorcery card from your opponent's graveyard. (I suppose Ancestral Recall or Brainstorm would be an exception.) The original intent of this card was to stop the spell and change/morph it into another spell. After looking at Oracle wordings for similiar effects, I decided this was the best way to do that. Compare with Desertion and
Spelljack. Also, it is intended that you must play the instant or sorcery card on resolution of this spell, if that makes sense. I wanted to avoid something like "If it's an instant or sorcery spell,
until end of turn, you may play target instant or sorcery card in that spell’s controller’s graveyard as though it were in your hand without paying its mana cost..."