Well, there are far too many combinations of decks in the new modified that can be good. That is why it's my favorite format, I've thought off about 5 Ex-On decks and all are pretty good in my mind, and for a card game to establish such variety equals awesomeness in my opinion.
One of the good decks already established is Gardevoir EX, overused maybe, but one has to admit, it's a pretty awesome deck.