Not good for Pox. Too mana intensive. You're hoping your opponent plays a creature that spells "I win" so you can steal it. If your Pox deck is built to handle creature threats, which it should be, then it will end up being a dead card. Since most Pox decks like to run Innocent Blood (best 1cc removal imo) you could be forced to sac it.
Worst case, it's the only threat in your hand and your opponent's threats all died to your removal.