Impostor Prof. Oak works in more than just Stall Decks.  If you have one in your hand, all you have to do is wait for your opponent to give some sign he or she has a good card.  True, some players can keep a perfect poker face.  However, others may flash a quick smile or even tell you what they have.  Yes, I have had people do that.  Consider this.  Your opponent draws a card.  Then she puts a Magikarp on her bench and puts a water energy on it.  There's a good chance she has a Gyrados in her hand.  Using an Impostor Prof. Oak forces her to discard it, giving you more time.  In conclusion, while Impostor Prof. Oak is not the best trainer around, he can be useful in more than stall decks.  If anyone wants to e-mail me my address is Woof246@aol.com