Yes that is true but if they SR first turn then you can hit them back with the proper attack (Mirror or Counter) since it is obvious what most types of attacks a lead uses. For instance you could keep Countering a Metagross until he attacks. If he wants to go on a PP stall then you can just encore his set up move (SR).
For trick leads if you encore them then they have to trick you again, taking back the scarf that they gave you (remember switching out isnt an option :D) but sleep leads still mess Wynaut up.
But yea I agree the most powerful part would be suprise factor if anything. I remember when I first saw it in Ubers I said WTF