@ sIKE
Agreed. If I'm playing against a mage with enchantments I would certainly test the waters before committing so much to the card. You'll need 18 Mana to counter an unknown card and still use Drain Soul. With nullifies and reverse magic there are plenty of throwaway curses (the best being Maim Wings maybe). At least with Reverse Magic you can't get hurt, but they still gain life and you lose mana. Losing that much mana could lose you the whole game. You're right about playing it at random times. I think that better insures you get the spell to cast.