Shen: Mewtwo is too easy to play around. It has to be on the field a turn in order to be a threat, SO I just snipe it with Palkia b4 it hits the field. That, and most people have given up on Mewtwo Lv. X because it just isn't that effective against most SP decks.
Lol, I played against a guy at BR's that said the same thing when I was trying the deck. I know him so I know he's playing Legos already... I mulligan once with Mew2 Lv. X in my hand and he sees it and he goes "That's cute." He's a bit of a know it all, so he goes on about how it's no prob (Almost word for word with the first part of your post IIRC), confident that he could tell me and still get around it. I won, lol.
It's still possible to get Mew2 out. Wait for the opponent to drop 80 on something, and lay down a Mew2. They can't KO it now, next turn promote it and Level Up. This is even more effective early game (When Mew2 SHOULD be coming out). And Mew2 is still common, I saw many at Nats and even read about some in some reports... so anyone with that attitude would lose to a Mew2 tech (I think people actually count on the "Mew2 is dead" attitude).