It makes Hourglass practically obsolete. Ten turns of this = 20 cards drawn. If it's in play from the word 'go' and doesn't cost me anything, I'll still run a small deck. It will just be much faster.
This card would make the super aggressive decks insanely fast, so you would have to have an even faster control setup to deal with it. Larger decks would be possible and maybe even more playable, but I only see the tight decks benefiting the most from a card like this. I can't see any scenario where this would help the game.
On the bright side, I think it's a really neat idea... just not really what the game should have atm.