It's a terrible first turn counter, but it becomes really awesome as the game progresses. I can see this easily being as good as Mana Leak in the midgame and much better as the game matures. It would probably be very, very good in limited. I'm not sure if there is an appropriate cost for this. It doesn't seem to merit
{U} (it feels like it should be splashable), but
still seems undercosted to me, while
seems overcosted. I guess it depends on how good you want to make it, but
is probably the right place for a playable card that requires a lot of strategy to play with well.
My real concern, by the way, is not that by costing just
, you can maximize this spell's utility. Control decks tend to keep their mana open until the end of their opponents' turns anyhow, so that's not really an issue. However, it used to be that an opponent with at least two untapped Islands was threatening a counterspell. This makes it so that even a single untapped island (along with N other untapped lands, which I reiterate, is not rare for a control deck to have) threatens a potent counterspell. This is particularly important because the current state of the art of countering is probably Hinder, which still requires double-blue and doesn't leave the control player open to doing things later in the turn, after having countered.
