Oh boy, EX cards for XY? It's obvious to me that there will still be Mega-Evolutions, what else would those mystery cards be? And there's an M in what looks to be the name of a mystery card.
I guessed we would have Mega-Evolutions as the ultra-rares instead but both EX AND Mega-Evolutions? I'm not so sure. EX cards are some of the rarest and most powerful cards at the moment and to add another tier? A bit ridiculous in my opinion. I'd settle for Mega-Evolutions on their own. I bet Mega-Evolutions will be equivalent to FA or SR cards. As mentioned by signofzeta, every group of card sets previously has had a maximum of 1 ultra rare pokemon card type (exception of Legends?). If there are only a few per set (e.g. just Mega-Venusaur, Mega-Charizard, and Mega-Blastoise as the 3 for the first set) then I don't mind. Otherwise EX cards would have to be a bit more common to allow players to collect these cards to play them (like normal basic/stage1 cards are more common than their evolutions).
And the fact that some Pokemon have 2 different Mega-Evolutions also is a bit of a problem. Which one will they use? Do both versions apply to the 4 card rule? And so on. I'm also not fond of having 2 versions of Mega-Evolutions. As much as I love both Mega-Charizards I'm annoyed at the unnecessary segregation which also affects the TCG making more versions of the same card (don't we all hate Litwick?), even though the Pokemon are slightly different. I would have preferred a Swanna in PB rather than a second non-holo Machamp.
On the other hand at least this allows Legendary Pokemon to still be able to have ultra rare cards. Best case scenario is that both the EX and normal versions of a pokemon can Mega-Evolve and that Mega Evolutions are the equivalent of FA cards but there are only a few per set. I prefer sets to have few ultra rares as it makes them all the more valuable to collect.
Anyhow I like the looks of these EX cards. I'm guessing the Mega-Charizard being segregated is the reason why it didn't appear with these cards. Jungle Hammer seems a bit underpowered for 4 energy but it heals 30 so all is not lost. No absolutely overpowered moves which is a good thing. I'm surprised that Xerneas does bench damage being a fairy type. I would have expected it from Yveltal instead. We still have no idea of what sort of mechanic Fairy type cards will use.