Me thinks Flygon/Flygon Lv. X are definitely the best cards revealed from the set so far. But thats not to say that I think they're super strong cards or broken by any means.
Gallade Lv. X definitely looks interesting. Especially when u consider all the other damage spreading pokemon around, lots of good supporting Galactic pokemon to go with it, and lots of good Galactic trainer cards to go with it(like the scoop up one). However, i think this cards biggest downfall is its weakness, Psychic x2 isnt a good thing to have these days with Gengar, Dusknoir, and AMU running around.
Overall, so far Im pretty unimpressed with the cards revealed from the set.